补偿性的工资差别
参考答案：
以高工资补偿恶劣的工作而形成的工资差别。
---Does your brother serve in the army?
---No, not now. But he ________ in the army for 8 years.
A．would serve
B．was serving
C．had served
D．served
造成合成催化剂温度升高的原因有（）。
A.入塔氨含量升高
B.新鲜气流量升高
C.冷激气量升高
D.惰气含量升高
