<正>Why do koalas sleep so much?为什么考拉那么爱睡觉?Koalas only eat tree leaves.Those leaves have a small amount of energy (能量).Koalas need to sleep a lot to save energy.Why do we yawn?我们为什么会打哈欠?
科研之友
微信
新浪微博
Facebook
分享链接
