About 10 bike-sharing companies have gone broke since last September,

About 10 bike-sharing companies have gone broke since last September, ______failing to return deposits to users and their deserted bicycles crowding sidewalks.
A．some of which B．some of them C．of which some D．which of them
【答案】B
【解析】考查独立主格。句意：自去年九月起大约有10家共享单车公司倒闭，他们中有一些没有归还使用者的押金，并且他们废弃的自行车堆满了人行道。分析句子可知，逗号之后是独立主格结构，用them代指上文的bike-sharing companies，故选B项。