---He made up his mind to devote his life________pollution_______happily.

A．to prevent;to live

B．to prevent;from living

C．to preventing; to live

D．to preventing;from living

拍集体照时，发现有人没进入镜头，应调节照相机，使（　　）

A．物距增大，使照相机镜头后缩

B．物距减小，使照相机镜头后缩

C．物距增大，使照相机镜头前伸

D．物距减小，使照相机镜头前伸