Một mạch điện xoay chiều nối tiếp gồm tụ điện có điện dung C, điện trở thuần R và cuộn cảm thuần có cảm kháng 80 Ω . Độ lớn hệ số công suất của đoạn mạch RC bằng hệ số công suất của cả mạch và bằng 0,6. Điện trở thuần R có giá trị

A.  50 Ω

B.  30 Ω

C.  67 Ω

D.  100 Ω

Read the following passage and mark the letter A, B, C or D to indicate the correct word or phrase that best fits each of the numbered blanks from 31 to 35.

KEEPING FIT

          Bodies are made to move! They are not (31) ________ for sitting around in front of the television or reading magazines. Keeping fit doesn't mean have to be a super-athlete, and even (32) ________ exercise can give you a lot of fun. When you are fit and healthy, you will find you look better and feel better. You will develop more energy and self-confidence.

Every time you move, you are exercising. The human body is designed to bend, stretch, run, jump and climb. (33) ________it does, the stronger and fitter it will become. Best of all, exercise is fun. It's what your body likes doing most-keeping on the move.

Physical exercise is not only good for your body. People who take regular exercise are usually happier, more relaxed and more alert than people who sit around all day. Try an experiment-next time you are in a bad mood, go for a walk or play a ball game in the park. See how much better you feel after an hour.

            A good (34) ________of achievement is yet another benefit of exercise. People feel good about themselves when they know they have improved their fitness. People who exercise regularly will tell you that they find they have more energy to enjoy life. So have (35) ________you'll soon see and feel the benefits

Điền vào ô 32

A. a little

B. a few

C. little

D. few