I think _______ impresses me about his painting is the colours he uses.
A. what B. that
C. which D. who
Some people believe _______ has happened before or is happening now will repeat itself in the future.
A. whatever B. whenever.
C. wherever D. however
Exactly______ the potato was introduced into Europe is uncertain, but it was probably around 1565.
A. whether B. why
C. when D. how
_____we understand things has a lot to do with what we feel.
A. Where B.How
C.Why D. When
—I wonder _________ Mary has kept her figure after all these years.
—By working out every day.
A. where B. how
C. why D. If
The exhibition tells uswe should do something to stop air pollution.
A. where B. why
C. what D. which