下列哪个为大气污染的最主要来源（）。
A.工业企业
B.生活炉灶
C.交通运输
D.采暖锅炉
E.乡镇企业
参考答案：A
A firm is most likely to structure a lease as an operating lease rather than a capital lease, when it:（）
A. has a high debt-to-equity ratio.
B. is very profitable.
C. does not have debt covenants.
放空管的直径应（）瓦斯主干管路的直径。
A.等于
B.大于
C.等于或小于
D.等于或大于
