--- How about the price of these washing machines? --- They are at least equal in price to

问题补充：

--- How about the price of these washing machines?

--- They are at least equal in price to, if not cheaper than, at other stores .

A. others

B. ones

C. that

D. those

答案：

A. others

B. ones

C. that

(答案→)D. those

解析：if not cheaper than为插入语，相当于if they are not cheaper than those at other stores。