A tourist will easily lose his way in Shanghai he has a map or a guide.A. ifB. sinceC. whi

问题补充：

A tourist will easily lose his way in Shanghai he has a map or a guide.

A. if

B. since

C. while

D. unless

答案：

A. if

B. since

C. while

(答案→)D. unless

解析：句意：除非旅游者有向导或者是地图，否则很容易在上海迷路。if如果，since自从，while在...期间，unless除非。根据句意，可知选D。