A:what those
B:that of those
C:that all of
D:which of those
已知样本容量是40,在样本的频数分布直方图中各小矩形的高之比依次为3:2:4:1,则第二小组的频数为____,第四小组的频率为____.
0.5÷0.9____0.5
0.55×0.9____0.55
36÷0.01____3.6×100
7.3÷0.3____73÷3.