燃气的质量指标包括（）
A、热值
B、烃露点
C、水露点
D、硫含量
E、二氧化碳含量
参考答案：A, B, C, D, E
Nowadays，it is common to see people staring at their mobile phones instead of reading a real book，＿＿＿＿＿＿many experts are worried．
A．when
B．for which
C．where
D．about which
传动比
