Electric current can be transmitted from the power station to where _______.

A.needed

B.is needed

C.needs it

D.it is needing

答案及解析： A

解析：

句中where引导的是宾语从句，此空填needed，其前省略了it is，it代替Electric current.因从句主语是谓语动词动作的承受者，从句应用被动语态.从句中省略了与主句相同的主语和be动词，只剩下构成被动语态的过去分词.C、D项是主动语态，与句意不符.这句意思是“电流能够从电站被输送到所需要的地方”.答案为A.