问题
I am ________ both speaking and writing.[ ]
A:concentrated
B:concentrating
C:concentrated on
D:concentrating on
B:concentrating
C:concentrated on
D:concentrating on
正确答案是：
同类题型
Your return ticket is________for three months.[ ]
(2013·北京东城区高三教学统一检测)He is, how shall I ________， not fat but rather well built.
The police recommended that the ________ in the accident ____________ to the hospital nearby at once
146. What a pity it is that Bob ______ the habit of smoking at such an early age!