蝉蜕的形成实际上是蝉在发育过程中的一种_________现象，是因为蝉体外的_________不能随着身体的长大而长大。
蜕皮 外骨骼
如图所示的四个情景中，属于光的直线传播形成的是（ ）
A．
城市夜空的光柱
B．
建筑物在水中的倒影
C．
公路转弯镜中的像
D．
透过鱼缸看到水中的鱼
Do you still remember the key points that _______ in his report? I don't remember them all. [ ]
A. referred to
B. were referred
C. he was referred to
D. were referred to
