It has been proved _______ eating vegetables in childhood helps to protect you against serious illnesses in later life.

A．if

B．that

C．what

D．when

一次性使用无菌注射器其镉的含量应是（）

A．≤10μg/g

B．≤5μg/ml

C．≤1.0μg/ml

D．≤0.5μg/ml

E．≤0.1μg/ml