下列X线防护方法中利用距离防护的是（）

A.使用铅橡皮手套

B.缩小胶片距离

C.增加X线源与受检者的距离

D.墙壁使用不透光物质

E.使用遮光筒和光圈

The helicopter deck of a ship must be marked with the units identification，appropriate aiming circles，and a continuous line on the perimeter which is（）.

A.8 inches wide

B.16 inches wide

C.24 inches wide

D.32 inches wide