公司有8个C类子网，整个的IP地址范围为192.168.8.0～192.168.15.255。为减轻路由表的负担，管理员准备使用一条汇总路由来代替8条路由。请问，这条汇总路由应该是以下哪一个？（）

A.192.168.8.0/16

B.192.168.8.0/20

C.192.168.8.0/21

D.192.168.8.0/22

—Look! The tree is growing well. When _____?

—Three years ago.[ ]

A. was it planted          

B. did it plant  

C. will it be planted      

D. is it planted