第45至48題為題組
      Can you tell the difference between grasshoppers and locusts? There are hundreds of species of grasshoppers,but only a small handful of those are locusts. Typically, locusts exist in their "grasshopper phase"--they lead solitary lives； they're green and pretty unremarkable. But when environmental conditions are right--usually when there's a lot of rainfall and moisture, which is perfect for their breeding status--something dramatic happens. They change their physiology like brain and coloration. Instead of repelling one another, they become attracted to one another. If those conditions persist in the environment, they may start to march together in coordinated formations across the landscape, as might be expected in eastern Africa.
      In truth, locusts are ravenous eaters. An adult desert locust that weighs about 2 grams can consume roughly its own weight daily. A swarm of just 1 square kilometer can const sume as much food as would be eaten by 35,000people in a single day. What's worse, a generation of locusts can multiply twentyfold every three months. When they grow exponentially, food shortages and economic risk may arise shortly after their attack.      To prevent such crises, some steps are being taken to fight locust swarms. Among them, the most effective way involves mass aerial sprays of pesticides to kill locusts. But that's not ideal, given the adverse effect such chemicals have on biodiversity and human health. Besides, biopesticides have untapped potential in killing pests.One popular set of bio tools is insect-killing microbes, in particular green zombie fungi, which have been proven to be the most effective. Another innovative approach is locust harvesting. In February 2020, a community in Okara district advocated a movement, with "Catch locusts, earn money and protect crops" as a slogan. It worked wonders with tons of locusts collected. The locusts are high in protein content and vitamins. Accordingly, they can be used as a rich source of feed for poultry, fish, and other animals. Hopefully, with cooperation between local people and
neighboring countries, locust swarms can be efficiently controlled and harvests will be safe from their attacks.
【題組】45. What is the main purpose of this passage?
(A) To help people get a better understanding of the classification of locusts and their natural enemies.
(B) To specify the features of locusts and the ways to fight them.
(C) To inform people of the significance of locusts in terms of biodiversity.
(D) To persuade people not to use chemicals to wipe out locusts.