Take him a walk when you have time. [ ]
A. to
B. for
C. on
D. with
答案：B
--What is Mum doing now?
--She ________ some clothes. [ ]
A. washes
B. is washing
C. washed
D. has washed
用毛细管比重瓶重复测定不易挥发又不很粘稠的油样的相对密度，最后两个结果之差应不大于（）才是可以接受的。
A.0.001
B.0.0006
C.0.0002
D.0.0001
