[讨论]OG-137

137. In 1982 the median income for married-couple families with a wage-earning wife was $9,000 more than a family where the husband only was employed.

(A)  a family where the husband only

(B)  of a family where only the husband

(C)  that for families in which only the husband

(D)  a family in which only the husband（C）

(E)   those of families in which the husband only

我的问题是，为何这里Family要用复数？当然可以参考未画线部分做到平行。但是难道income, husband不应用复数了吗？还是这样会造成搞不清楚，造成一个Family会有多个husband？但我觉得这里用单数好像也说不过去，难道families 只需一个husband, income?

谢谢