Select the most appropriate word to fill in the blank.
This is only a partial list of the books ___________ are needed in the library.

The correct answer is (b) that.
Explanation:
The correct relative pronoun here is "that," which refers to the subject "books" (plural). "That" is used to introduce a defining clause, indicating which books are needed in the library.
Meanings of all options:
· That's: Contraction of "that is," which is grammatically incorrect in this context.
· That: A relative pronoun used to introduce a defining clause.
· Those: Demonstrative pronoun, which does not fit grammatically in this sentence.
· Their: Possessive pronoun, which is incorrect in this context.