What is the antecedent for (words)

In grammar, an antecedent is a word that another word refers back to. That word is technically called a proform, and while English allows for types of antecedents based on many parts of speech, such as pro-verbs and pro-adverbs, it is far more common for a pronoun to refer to an antecedent.

Explanation:

1.c

2.a

3.d