各气瓶以及回火防止器、减压器等的解冻方式是什么？
参考答案：只许用热水或蒸汽解冻。
Isabel is very happy because she has _ friends in Beijing. [ ]
A. few
B. a few
C. much
D. little
( )是国际贸易中使用最为广泛的提单。
A．清洁提单
B．备运提单
C．指示提单
D．转船提单
