Pronouns
If a noun serves as an unchanged subject in a continuous discourse, its later appearances in the ensuing clauses or sentences generally should be substituted by an appropriate pronoun or simply omitted. The pronoun, in turn, can also be omitted after its first appearance.
Question Pronouns
Question pronouns include 谁, 什么, 那, 哪儿, 几, etc. In a question with a question pronoun, the word order is exactly the same as that in a declarative sentence. When forming a question with a question pronoun, start with a declarative sentence and then replace the part in question with the appropriate question pronoun.
Ex) 那个人是谁?
Ex) 那个人是谁?