目前驱动装置的电机有步进电动机、直流伺服电动机和交流伺服电动机等。
参考答案：对
液化石油气由液相变为气相，体积扩大约250倍，易与空气形成爆炸性混合物，爆炸极限通常为1.5%～18%。（）
We _____ last night, but we went to the concert instead. [ ]
A. must have studied
B. might study
C. should have studied
D. would study
