受精的鸟卵在雌鸟体内开始胚胎发育，但是鸟卵产出后就停止发育，影响发育的因素是（　　）

A．阳光

B．空气湿度太低

C．空气污染

D．温度太低

If the officer on watch is in any doubt as to the pilot’s actions,or intentions,he should（）.

A.notify the captain as soon as possible

B.seek clarification from the pilot

C.take action by his own judgment

D.cease the duty of pilot's at once