问题补充：
— Excuse me . I’m looking for Be the Best of Yourself .
— Sorry . The book you ask for out .
A. is selling
B. is sold
C. was selling
D. will be sold
答案：
A. is selling
(答案→)B. is sold
C. was selling
D. will be sold
解析：句意：打扰您一下。我在找《做最好的自己》。对不起。你要的那本书已经卖完了。Sell out售完，脱销。根据句意可知该用一般现在时被动语态，所以选B。
