练习说明
句子填空 题目要求：阅读文段，从文中挑选原词补全句子，每道题目都有特定的字数要求，以黑体加粗字标示。请把答案填到每题空缺处。
Choose NO MORE THAN TWO WORDS from the passage for each answer
第 1 题
Some time in the early Cretaceous period of the Earth's history, hunting wasps of a certain type became bees by adopting a vegetarian diet: they began to rely more and more on the pollen of plants as a source of protein for themselves and their offspring, as an alternative to insects. In so doing, they accidentally transported pollen on their bodies to other plants of the same species, bringing about pollination.
Hunting wasps used to feed on other ......................, rather than on vegetation.
第 2 题
Flowering plants started to reward bees with rich pollen and an additional food in
第 3 题
Today about 15 per cent of our diet consists of crops which are pollinated by bees. The meat and other animal products we consume are ultimately derived from bee pollinated forage crops, and account for another 15 per cent. It follows that around one third of our food is directly or indirectly dependent on the pollinating services of bees.
Approximately ...................... of human food production relies on the activity of
第 4 题
Clearly a species which depends on cross-pollination is on a knife-edge: it must provide sufficient nectar to attract the interest of a bee, but not enough to satisfy all of its needs in one visit. A satiated bee would return to its nest rather than visit another flower.
If the process of ...................... is to take place effectively, bees need to travel from
第 5 题
The bee, on the other hand, is out to get the maximum amount of pollen and nectar. It must assess the quality and quantity of rewards which are on offer and juggle its energy costs so that it makes a calorific profit on each foraging trip. The apparent harmony between plants and bees is therefore not all that it seems. Instead, it is an equilibrium based on compromises between the competing interests of the protagonists.
Bees need to balance the ...................... of each trip against the calorific rewards
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