异步电动机的调速性能比直流电动机要好。
参考答案：错
— You________have finished your composition.
— I had meant to, but before I could, the bell rang and we had to hand in our test papers. [ ]
A. were supposed to
B. were able to
C. had to
D. were determined to
发生锅炉爆炸的单位，应再事故处理后按时逐级上报。（）
