下列原理中不能用于速度测量的是( )。
A．散热率法
B．动压法
C．霍尔效应
D．激光多普勒效应
参考答案：C
________ at the theatre, he found the ticket his friend gave him was left at home. [ ]
A. To arrive
B. On arriving
C. While arrived
D. On arrived
