问题：
One advantage of G3 mobiles is that it has become a very useful tool for________daily communication.
[ ]
A. taking on
B. speeding up
C. working on
D. making up
One advantage of G3 mobiles is that it has become a very useful tool for________daily communication.
B. speeding up
C. working on
D. making up
[ ]
A. taking on B. speeding up
C. working on
D. making up
参考答案：