一、单项填空（共15小题，每小题1分，满分15分）
从A、B、C、D四个选项中，选出可以填入空白处的最佳选项。
1. — Have you seen _____ empty box?
— Do you mean _____ box you showed to me yesterday? I put it in your schoolbag.
A. a, the B. an, a C. an, the D. the, a
2. —Have you found your lost mobile phone?
—No, I haven’t. But I bought ________ yesterday.
A. it B. one C. another D. other
3. Li Feng’s __________ of devotion to others will be remembered not only in China
but also in some other parts of the world.
A. achievement B. service C. thought D. spirit
4. I don’t have to introduce him to you ________ you know the boy..
A. until B. unless C. since D. but
