题目内容：
Itcan be inferred from the physical phenomenon that_______.
A． theforce of the electromagnetic field is too weak to be harmful A．the force of the electromagnetic field is too weak to be harmful
B． theforce of the electromagnetic field is weaker than the electric field that thecells generate
B． the force of the electromagnetic field is weaker than the electric field that the cells generate
C．electromagnetic field may affect health
C．electromagnetic field may affect health
D． onlymore powerful radiation can knock electron out of human body
D． only more powerful radiation can knock electron out of human body
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