reason定语从句

for that
请帮我解答一下并说明理由.what C，谢谢.why DIs that the reason ___ you are in favour of the poroasl?
A.which B

那什么时候用that?

选C
which用在先行词reason的后面一般为for which
what不用于定语从句
这种句式没有for that的用法
why=for which

选C是正确的, 但the reason后不一定接why 例如:The reason you gave me seems impossible.

C the reason …why..固定搭配

选b，因为关系副词why只能做从句的状语，关系代词that可以做主语宾语表语。看清楚从句缺少的成分就可以很容易的选出来了。