The Waller stein study indicates that even after a decade young men and women still experience some of the effects of a divorce occurring when a child.
A occurring when a child
B occurring when children
C that occurred when a child
D that occurred when they were children
E that has occurred as each was a child
我觉得是因为前面的成分太多了,Waller stein 的研究指出 young men and women 仍受到儿时父母离异的影响,一般省略主谓都是在主句成分比较少,主谓比较明确的时候。如果省略的主语是 Waller stein ,语法上也是说得通的,但是语义上比较不合理。我觉得一般这种有强调某些部分的,比如被省略的,或者被用代词代替的成分,但凡在其他选项里被强调了最好别图省事。完整的总不会错。