The authorities declared that because of the war petrol was _____ and had to be rationed (定量供应).

Polar bears live _____on sea ice, which they use as a platform for hunting seals [ ]

What do you think of the book A Haw Treewritten by a woman writer—It reminds me of the days ________ I spentin the countryside.

If we want to work for our country in the future，________，we should have a strong body and rich knowledge．

You’d better go there by train. The train ticket is_____ the airplane ticket.