随机抽样的目的是（）。

A.消除系统误差

B.消除测量误差

C.消除系统误差和测量误差

D.减少随机误差

E.减少样本的偏性

— Which one do you want to buy, an ipod touch 4, an ipad 3 or an iphone 5?

— _____. They are too expensive.[ ]

A. All

B. Both

C. None

D. Neither