Professor: Whales carefully conserve their oxygen when underwater in a couple of ways. When a whale dives, its metabolic rate drops, causing its heartbeat to slow down. And the blood flow to its muscles and some of its non-vital organs, like its kidneys, is also cut off. 鲸鱼在水下有很多储存氧气的方法：潜水时，鲸鱼代谢率下降导致心跳速度降低，血液流向肌肉，某些不重要器官的血流量会被切断。由此可知选项A 和 D 正确。

答案: AD