问题补充：
The book well. I’m afraid it out.
A. is sold; has sold
B. sells; is sold
C. sells; to be sold
D. is sold; sells
答案：
A. is sold; has sold
(答案→)B. sells; is sold
C. sells; to be sold
D. is sold; sells
解析：句意：这本书卖得不错。我担心它已经卖完了。Sell可用作及物动词和不及物动词。其主语一般是指人，但是在表示某物卖得不错时，要用主动语态。结合语境可知下文主语是出售的对象，故用被动语态。上文表示某物卖得不错，故选D。
