請依下文回答第 21 題至第 25 題        Many people incorrectly think that all frogs are alike. In fact, there are hundreds of varieties ofthese __21__ , which can live both on land and in water. The many types of frogs vary not only in sizesand colors but also in their abilities to survive in and __22__ to different environments. For example, thegreen tree frog can change the color of its skin from tan to green to gray to yellow. This enables the frogto hide from its enemies wherever they are __23__ . Another interesting example is the poison arrow frog,which is very dangerous. This frog’s skin contains a poison powerful __24__ to kill many larger animalsthat touch it. The frog also has a red stomach. When an enemy is near, the frog rolls__25__ its back. Thebright red color usually scares the enemies away. These two examples illustrate how different frogscan be.
【題組】21
(A) mammals
(B) cannibals
(C) amphibians
(D) insects