the majority of people you will meet when travelling are sure to be friendly there are

问题补充：

the majority of people you will meet when travelling are sure to be friendly, there are dangers-theft being the most common.

A. Since

B. Unless

C. While

D. Once

答案：

A. Since

B. Unless

(答案→)C. While

D. Once

解析：考察连词辨析。A自从，既然；B除非，如果…不；C尽管，当…时；D一旦；句意：尽管在你旅行的时候所遇见的人当，大部分都是友好的，但是也有一些危险。故C正确。