从句式角度看,下列句子不同类的一项是 ( )
A:大王来何操?
B:若不阙秦,将焉取之?
C:沛公安在?
D:夫晋,何厌之有?
例:
He didn't fly a kite yesterday.
He did his homework yesterday.
用如图所示的装置探究凸透镜成像规律.凸透镜的焦距是15cm.当把凸透镜固定在50cm刻度线处,蜡烛固定在15cm刻度线处时( )