4.Yunnan province in China was attacked by such a terrible drought this early spring ________ few people had experienced before, _______ made us worry about global climate changes.
A. that; that B. as; which C. which; it D. when; as
5.28. He came from Russia, ______ I detected from his strong Russian accent.
A. that B. what C. as D. where
6.Every day we have to face new challenges and problems.Actually，stress isn’t such a bad thing___ is often supposed to be.
A.which B.as C.what D.that
7.Children are not recommended to see such films bad for their mental development.
A．that is B．that are C．as are D．as is