The radiation amount of a mobile phone for two half-hour periods per day is equal to to

问题补充：

The radiation amount of a mobile phone for two half-hour periods per day is equal to to an X-ray for ten seconds.

A. expose

B. exposing

C. exposed

D. being exposed

答案：

A. expose

B. exposing

C. exposed

(答案→)D. being exposed

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