已知在单摆a完成10次全振动的时间内，单摆b完成6次全振动，两摆长之差为1.6m．则两单摆摆长L_a和L_b分别为（　　）

A．L_a=2.5m，L_b=0.9m

B．L_a=0.9m，L_b=2.5m

C．L_a=2.4m，L_b=4.0m

D．L_a=4.0m，L_b=2.4m

— His brother is an army man.

— I heard that he got an increase in ______ recently. [ ]

A. salary

B. wages

C. pay

D. money