Co-operation or teamwork, the importance of which is often ________, plays an important part in football matches.

It’s easy to make friends, but it’s difficult to keep the ________ longer.

That was the only gate _____ we could rush out and save those _____ were in great danger.

The scientist was ______ in thoughts.[ ]

–You are lucky that she is very thoughtful and devoted to you.—— In fact, I don’t want to ____ her with my problems all the time.