---When shall we leave for Shanghai?
---We won’t we have visited all the places of interest in Nanjing.
A. until
B. while
C. as
D. since
网友回答
(答案→)A. until
B. while
C. as
D. since
解析：until 直到……才；while 然而，当……时； as由于，随着； since自从……以来；句意：我们什么时候动身去上海？——我们直到参观了南京所有有趣的地方才去。