若在低倍显微镜下用目镜侧微尺测量细胞长径(如图1),则转换高倍物镜后观察到的图像是
A:
B:
C:
D:
I sometimes play tennis for half hour.
关于O2与O3气体,下列比值一定为2:3的是( )
His cousin hardly has vegetables these days, __________?