The old man has four sons, and two _____ turned doctors.
. you like it or not, you'll have to give up smoking.
Your shirt needs ____. You'd better have it done today.
—Why is Mr. Li so happy this morning? —Because he was honoured with a(n)______ for excellence in teaching.
________ you are interested in astronomy, you can read the book.
After the new technique was introduced, the factory produced ______ tractors in 1998 as the year before.