and, as he begins to tire, she supports him close to the surface so that he can breathe more easily. 疲劳的幼鲸被妈妈托上浮上水面好让它呼吸空气
As the current begins to build, it's up, up and away. 洋流开始转强时它们就只好远走高飞了
As the vegetation in one place begins to run out 当一个地方的植物即将吃光时
Fishing practice begins when the cubs are four months old. 小水獭在4个月大时就开始学习捕鱼
and at 50 degrees of latitude a radical transformation begins. 北纬50°的地方是一场重大变革的起点