下列动物中，学习能力最强的是 [ ]

A．蚯蚓

B．大山雀

C．黑猩猩

D．牛

In my opinion, life in the twentyfirst century is much easier than           .    [ ]

A. that used to be    

B. it is used to    

C. it was used to    

D. it used to be