单选题 Due to a series of thefts, many technology companies need security personnel for ______ research facilities to protect their intellectual property.
【正确答案】 C
【答案解析】[解析] 语法：代词
1．这是一道词汇题，选项均为代词。
2．空格内须填入一个词修饰后面的名词facilities，物主代词their可作修饰词，因此C为正确选项。