If you swim in a river or lake, be sure to investigate is below the water surface. Often there are rocks or branched hidden in the water.

A. what B. who

C. that D. whoever

The exhibition tells uswe should do something to stop air pollution.

A. where B. why

C. what D. which

—I wonder _________ Mary has kept her figure after all these years.

—By working out every day.

A. where B. how

C. why D. If

_____we understand things has a lot to do with what we feel.

A. Where B.How

C.Why D. When

Exactly______ the potato was introduced into Europe is uncertain, but it was probably around 1565.

A. whether B. why

C. when D. how

Some people believe _______ has happened before or is happening now will repeat itself in the future.

A. whatever B. whenever.

C. wherever D. however

I think _______ impresses me about his painting is the colours he uses.

A. what B. that

C. which D. who

Among the many dangers_-- sailors have to face, probably the greatest of all is fog.

A. which B. what

C. where D. when

Grandma pointed to the hospital and said, "That's ______ I was born."

A. when B. how

C. why D. where

—What a mess! You are always so lazy!

—I’m not to blame, mum. I am ________ you have made me.

A. how B. what

C. that D. who