試題詳解

47. Animals' sleeping habits _________. They differ according to what time of day they sleep. Some animals sleep during daylight hours while others sleep during darkness. They also differ in the length of time they sleep. Other animals sleep for weeks or months at a time when they sleep through the winter.
(A) vary in a number of ways
(B) create different ecological systems
(C) change with their environment
(D) develop with their surroundings