【题目】She says that she'll have to close the shop ________ business improves.
A.if
B.unless
C.after
D.when

【答案】B
【解析】句意：她说她将不得不关掉商店，如果生意不提高的话。A. if如果，B. unless除非，如果不，C. after在…后面，D. when当…时候，选B。