对于各组份相对挥发度相差较大,沸点又较低的混合份应采用()。
A.减压蒸馏
B.一般精馏
C.萃取精馏
参考答案:B
He has many friends, but ________ are true friends. [ ]
A. a few
B. few
C. a little
D. little
房地产开发的最本质的特点是()
A.长期性
B.地域性
C.风险性
D.综合性