阅读下列材料，从A、B、C、D四个选项中选出最佳答案。

Big ears keep me cool!

The long-eared jerboa(长耳跳鼠) is about 10 cm long, not counting its long tail. Its ears are 3.8 to 5 cm long, taking up 40 to 50 percent of its body length.

Why does it have such big ears? Large ears help the long-eared jerboa to live in hot, dry environments. They can lose heat quickly through the large ears.

How many times does my heart beat?

Blue whales are the largest animals on the earth. When they are swimming underwater, their heart beats four to eight times every minute. When they go up to breathe, their hearts beat 25 to 37 times each minute.