【单选题】Why must the audience remain seated?
A.
The performance is being monitored.
B.
The performance is being broadcast.
C.
The performance is being videotaped.
D.
The actors can be disturbed.
【多选题】在下列各项中选出左旋仲丁醇和右旋仲丁醇不同的选项:
【单选题】数年前一位芬兰大学生在Internet上公开发布了一种免费操作系统_________,经过许多人的努力,该操作系统正不断完善,并推广应用。
【单选题】数年前一位芬兰大学生在Internet上公开发布了一种免费操作系统_________,经过许多人的努力,该操作系统正不断完善,并推广应用
【单选题】Hardly ______ when the lights went out.
A.
the performance had begun
B.
had the performance begun
D.
did the performance begin