The government claimed that tax cuts benefited the poor most，___

The government claimed that tax cuts benefited the poor most，_____________ has yet to be proved in practice.
A、 it
B、 who
C、 that
D、 which
【正确答案】：D
【题目解析】：该题考查的是非限制关系分句。此分句前有逗号是个非限制关系分句，关系词指代前面的整句话，只能用which。