问题补充：
The computer looks old, but it just half a year ago.
A. has been bought
B. was bought
C. is bought
D. will be bought
答案：
A. has been bought
(答案→)B. was bought
C. is bought
D. will be bought
解析：考查时态。句意：这台电脑看起来旧了，但是它只半年前买的。结合语境可知下文描述的是过去的动作，故用过去时态，选B。
