我国黄土分布面积约为63万余km2，主要分布在（）三省。
A、湖北
B、甘肃
C、陕西
D、山西
E、四川
参考答案：B, C, D
．We are taught that a business letter should be written in a formal style ____ in a personal one．
A．less than
B．other than
C．better than
D．rather than
减压侧线温度的调节
