这题为什么选A?

问题描述:

这题为什么选A?
紧急!我下午要高考考英语
(  )26.They felt ________ it was high tax and low income ________ contributed to the extreme misery of the working people at the bottom of the ladder.
A./;that B.that; which C.that; what D./; which

They felt that it was high tax and low income that contributed to the extreme
这是一个强调句,句型是:it was.that