The laser is a very useful means for long-distance communications, the great accuracy in the direction of its beams ______ effective use of small amount of power.

A．makes

B．making

C．made

D．to make

头围是反映孩子大脑发育的重要指标，满1岁时头围约为（）

A、45～46

B、47～48

C、32～33

D、40～42