单选题 Not once in these years ______ the prices of these products.
A. we changed B. have we changed
C. did we change D. we have changed

【正确答案】 B

【答案解析】[解析] 本题考查的是倒装句型，否定词+倒装结构，例：Not once did he talk to me．意为：他一次也没有和我谈过。本题题意是：这些年我们一次也没有改变产品的价格。故本题答案为B。