甲数是a，比乙数的2倍多b，表示乙数的式子是（ ）
A．（a+b）÷2
B．（a-b）÷2
C．a÷2+b
D．a÷2-b
（a-b）÷2，
故选：B．
_____ time, he'll make a first-class tennis player.[ ]
A. Having given
B. To give
C. Giving
D. Given
