下面（）因素，可能影响精馏塔回流中断。
A、回流泵汽蚀
B、回流槽液位低
C、塔压高
D、塔压低
参考答案：A, B
ˉWhat do you think made Tom so upset?
ˉ ______her new bicycle.
A．Because of
B．Lost
C．As she lost
D．Losing
何谓多模光纤？何谓单模光纤？
