单选题 What did the supermarket promise its customers?
A. Free shopping for all customers.
B. Free shopping for all customers on a certain day.
C. Free shopping for one customer.
D. Free shopping for one customer once a week.

【正确答案】 D

【答案解析】事实细节题。题目问超市给顾客什么承诺。从文章第一段最后一句话“Remember, once a week , one of our customers gets free goods. This May Be Your Lucky Day!”，可以知道超市承诺的是：一周只有一名幸运顾客，所以D项是正确答案。