______________ about wild plants that they decided to make a trip to Madagascar for further research.

I arrived late; I _____ the road to be so icy

_______ we go to the McDonald’s I am sick ofthe food there!

Look,Mr.Hu is on the other side of the street. —-It____ be him.He has gone to Lanzhou.

When was it ______ you met Yao Ming in the street?