在爬升中遭遇冻雨常常表明什么？
参考答案：
在冻雨层之上存在一个更暖的空气层
_________ smoking, he would not have got cancer in the lung.
A．Was he given up
B．Had he given up
C．Did he give
D．If he gave up
GB 6653-94属于推行标准。
