The astronauts have to lie ________ the floor of thespaceship to fight against the great pressure during the flight.

The colors on the national flags can be ______ differently in different culture, but they have one thing in common, that is, ______of the colours was carefully chosen.

Was it in the factory_____ you worked five years ago___ you learned the technique?

Would you like to go birdwatching withus— .

It is ______ Tom often breaks the school rules _______ makes his teacher unsatisfied with him.[ ]