It is __________to visit so many places of ________around the world. I never feel _________when I see them.

rvey shows that ______ we are enjoying less and less good sleep, rates of heart diseases have risen rapidly．

is one of the best sports in summer, we boys all enjoy it.

Have you been to the Great Wall—Perhaps not in my memory; ________， it might have been during the early childhood.

These young trees must ______.