Questions 18-25 Complete the summary below. Choose NO MORE THAN THREE WORDS from the passage for each answer. Write your answers in boxes 18-25 on your answer sheet.
原文
D The project used two main remote-sensing techniques. The first is magnetometry, which works on the principle that magnetic fields at the surface of the Earth are influenced by what is buried beneath. It measures localized variations in the direction and intensity of this magnetic field. "The Earth's magnetic field can vary from place to place, depending on what happened there in the past," says Branting. "If something containing iron oxide was heavily burnt, by natural or human actions, the iron particles in it can be permanently reoriented, like a compass needle, to align with the Earth's magnetic field present at that point in time and space." The magnetometer detects differences in the orientations and intensities of these iron particles and uses them to produce an image of what lies below ground.
F The other main sub-surface mapping technique, which is still being used at the site, is resistivity. This measures the way electrical pulses are conducted through sub-surface soil. It's done by shooting pulses into the ground through a thin metal probe. Different materials have different electrical conductivity. For example, stone and mudbrick are poor conductors, but looser, damp soil conducts very well. By walking around the site and taking about four readings per meter, it is possible to get a detailed idea of what is where beneath the surface. The teams then build up pictures of walls, hearths, and other remains. "It helps a lot if it has rained, because the electrical pulse can get through more easily," says Branting. "Then if something is more resistant, it really shows up." This is one of the reasons that the project has a spring season, when most of the resistivity work is done.
Exploring the ancient city of Pteria
第 18 题
Archaeologists began work ten years ago. They started by taking photographs of the site from the ground and then from a distance in a _____ They focused on what lay below the surface using a magnetometer, which identifies variations in the magnetic field. These occur when the ____ in buried structures have changed direction as a result of great heat. They line up with the surrounding magnetic field just as a ____ would do. The other remote-sensing technique employed was resistivity. This uses a ____ to fire electrical pulses into the earth. The principle is that building materials like ____ and stone do not conduct electricity well, while ____ does this much more effectively. This technique is mainly employed during the ____, when conditions are more favourable. Resistivity is mainly being used to ____ some images generated by the magnetometer.
正确答案：hot-air balloon
第 19 题
Archaeologists began work ten years ago. They started by taking photographs of the site from the ground and then from a distance in a ____ They focused on what lay below the surface using a magnetometer, which identifies variations in the magnetic field. These occur when the _____ in buried structures have changed direction as a result of great heat. They line up with the surrounding magnetic field just as a ____ would do. The other remote-sensing technique employed was resistivity. This uses a ____ to fire electrical pulses into the earth. The principle is that building materials like ____ and stone do not conduct electricity well, while ____ does this much more effectively. This technique is mainly employed during the ____, when conditions are more favourable. Resistivity is mainly being used to ____ some images generated by the magnetometer.
正确答案：iron particles
第 20 题
Archaeologists began work ten years ago. They started by taking photographs of the site from the ground and then from a distance in a ____ They focused on what lay below the surface using a magnetometer, which identifies variations in the magnetic field. These occur when the ____ in buried structures have changed direction as a result of great heat. They line up with the surrounding magnetic field just as a _____ would do. The other remote-sensing technique employed was resistivity. This uses a ____ to fire electrical pulses into the earth. The principle is that building materials like ____ and stone do not conduct electricity well, while ____ does this much more effectively. This technique is mainly employed during the ____, when conditions are more favourable. Resistivity is mainly being used to ____ some images generated by the magnetometer.
正确答案：compass needle
第 21 题
Archaeologists began work ten years ago. They started by taking photographs of the site from the ground and then from a distance in a ____ They focused on what lay below the surface using a magnetometer, which identifies variations in the magnetic field. These occur when the ____ in buried structures have changed direction as a result of great heat. They line up with the surrounding magnetic field just as a ____ would do. The other remote-sensing technique employed was resistivity. This uses a _____ to fire electrical pulses into the earth. The principle is that building materials like ____ and stone do not conduct electricity well, while ____ does this much more effectively. This technique is mainly employed during the ____, when conditions are more favourable. Resistivity is mainly being used to ____ some images generated by the magnetometer.
正确答案：thin metal probe
第 22 题
Archaeologists began work ten years ago. They started by taking photographs of the site from the ground and then from a distance in a ____ They focused on what lay below the surface using a magnetometer, which identifies variations in the magnetic field. These occur when the ____ in buried structures have changed direction as a result of great heat. They line up with the surrounding magnetic field just as a ____ would do. The other remote-sensing technique employed was resistivity. This uses a ____ to fire electrical pulses into the earth. The principle is that building materials like _____ and stone do not conduct electricity well, while ____ does this much more effectively. This technique is mainly employed during the ____, when conditions are more favourable. Resistivity is mainly being used to ____ some images generated by the magnetometer.
正确答案：mudbrick
第 23 题
Archaeologists began work ten years ago. They started by taking photographs of the site from the ground and then from a distance in a ____ They focused on what lay below the surface using a magnetometer, which identifies variations in the magnetic field. These occur when the ____ in buried structures have changed direction as a result of great heat. They line up with the surrounding magnetic field just as a ____ would do. The other remote-sensing technique employed was resistivity. This uses a ____ to fire electrical pulses into the earth. The principle is that building materials like ____ and stone do not conduct electricity well, while _____ does this much more effectively. This technique is mainly employed during the ____, when conditions are more favourable. Resistivity is mainly being used to ____ some images generated by the magnetometer.
正确答案：damp soil
第 24 题
Archaeologists began work ten years ago. They started by taking photographs of the site from the ground and then from a distance in a ____ They focused on what lay below the surface using a magnetometer, which identifies variations in the magnetic field. These occur when the ____ in buried structures have changed direction as a result of great heat. They line up with the surrounding magnetic field just as a ____ would do. The other remote-sensing technique employed was resistivity. This uses a ____ to fire electrical pulses into the earth. The principle is that building materials like ____ and stone do not conduct electricity well, while ____ does this much more effectively. This technique is mainly employed during the _____, when conditions are more favourable. Resistivity is mainly being used to ____ some images generated by the magnetometer.
正确答案：spring (season)
第 25 题
Archaeologists began work ten years ago. They started by taking photographs of the site from the ground and then from a distance in a ____ They focused on what lay below the surface using a magnetometer, which identifies variations in the magnetic field. These occur when the ____ in buried structures have changed direction as a result of great heat. They line up with the surrounding magnetic field just as a ____ would do. The other remote-sensing technique employed was resistivity. This uses a ____ to fire electrical pulses into the earth. The principle is that building materials like ____ and stone do not conduct electricity well, while ____ does this much more effectively. This technique is mainly employed during the ____, when conditions are more favourable. Resistivity is mainly being used to _____ some images generated by the magnetometer.