-- Do you know everyone from Class One?-- Er… I know some of .A. they B. them C. their

问题补充：

-- Do you know everyone from Class One?

-- Er…, I know some of .

A. they B. them C. their

答案：

解析：句意：你知道一班的每个人吗？……，我知道他们中的一些。所填词指代上文中的everyone，并且跟在介词of之后，该填宾格的人称代词，所以选B。