Once environmental damage _______,it takes many years for the system to reca、has done b、is to doc、 does d、is done

问题描述:

Once environmental damage _______,it takes many years for the system to rec
a、has done
b、is to do
c、 does
d、is done

选D。这题是被动语态,用动词的过去分词表被动。

选D,对应后面半句的时态,是一般现在时

D