下面是一些生物的归类方法,将两部分连线。
一条路长20米,在路的一旁从头到尾每隔5米栽一棵树,共要栽( )棵树。
We wanted to know _____. [ ]
A. where did he live three years ago
B. where he lived in three years before
C. why he cried so sadly
D. how soon he will come back