With more than 17000 islands, ________ only 6000 are inhabited, Indonesia is the world's largest archipelago(岛国)．

A.on which

B.for which

C.of which

D.along which

答案及解析： C

解析：

“超过17000个岛屿，其中只有6000个有人居住，印尼是世界上最大的岛国。介词加which构成的定于从句，相当于only 6000 of the 17000 islands are inhabited，用of which 来表示。