石油钻机按运输方式分为车装钻机、拖挂钻机、块装钻机和直升飞机吊装钻机。
参考答案：对
—Oh, my God! We have missed the last bus. What shall we do?
—I'm afraid we have no _______ but to take a taxi. [ ]
A. decision
B. choice
C. advice
D. reason
三相交流电与单相交流电相比有何优点？
