Which of the highlighted verbs could be in the present perfect in this dialogue? Choose as many as you think are possible to say in the present perfect.– I’m sorry tosayyour wifehadan accident.– Oh no! Whathappened?– Shewasin a car crash.–Isthe car OK?– I’m afraid not!
A. happened
B. had
C. say
D. was
E. is
查看答案
If your friend says, “I’ve eaten all five cakes,” which sentences describing present consequences are likely to be true?
A. Now there are no cakes.
B. Your friend is probably not hungry.
C. There are five cakes left.
D. Your friend feels ill.
E. Your friend wants to eat more.
F. The cakes are delicious.
带传动的中心距与小带轮的直径一定时,若增大传动比,则小带轮上的包角()。
A. 减小
B. 增大
C. 不变
D. 与传动比无关
设计V带传动时,采用A型V带时,带根数过多,可采用()来解决。
A. 增大传动比
B. 减小中心距
C. 改选B型V带
D. 改选Z型V带
起重机对电气传动的要求有:调速、平稳或快速起制动、纠偏、同步保持、机构间的动作协调、吊重止摆等。
A. 对
B. 错