What type of pronoun appears in all capital letters These are the documents THAT will be most useful?

The pronoun in all capital letters is THAT. This pronoun is a relative pronoun.

Here's why:

* Relative pronouns connect a dependent clause to an independent clause. They refer back to a noun or pronoun in the main clause.

* THAT in this sentence refers back to "documents" and introduces the dependent clause "THAT will be most useful".

Let me know if you'd like to explore other types of pronouns!