常用普通离心机为每分钟多少转?()
A.1000~9000转/分钟
B.20000转/分钟
C.30000转/分钟
D.50000转/分钟
E.100000转/分钟
参考答案:A
If we can _____ our present difficulties , then everything should be all right . [ ]
A. come across
B. get over
C. come over
D. get off
线型无定形聚合物常存在的三种物理状态:()()()