The United States is composed of fifty states, two of _____are s

The United States is composed of fifty states, two of _____are separated from the others by land or water.


A、them
B、that
C、which
D、those
【正确答案】：C
【题目解析】：在非限制性定语从句中，关系代词前面可能会有介词，在介词前面还可能有其他限定词，这就更复杂一些，需特别注意。