A:used to have
B:is used to having
C:is used for having
D:is used to have
我能连线。
小燕子____ 忙着搬东西
小鱼____ 忙着捉虫子
小蚂蚁____ 到水面上透气
-_____ do you _____ the book?
-It's very interesting.