精馏塔的全回流是指塔顶馏出物经冷凝后全部作为塔的回流，塔顶没有采出。
参考答案：对
美国以外的所有银行费用由（）负责。
A．受益人
B．开证人
C．开证银行
The number of people invited _____ fifty, but a number of them _____ absent for different reasons.
[ ]
A. were; was
B. was; was
C. was; were
D. were; were
