My grandfather is over seventy years old, he is very well because he always____.

A．drinks tea

B．sleeps late

C．plays computer games

D．takes exercises

锁止离合器在（）、（）等条件满足时，将泵轮和涡轮锁定在一起，使变矩器内的动力传递由液力传递变为机械传递，传递效率达到100%。