What type of word indicates a noun will soon follow?

It's called an article (The,an, a). Adjectives may work but not always.

For example,
The road is wet.

The noun went first before the adjective. This can be rearranged into the following statement.
The wet road.

For both statements, the article comes first before the noun.

The case type pronoun that is required to complete the sentence would be A) nominative. It is the subject case, and since we need a subject here, nominative is the option we have to use. For example:
They and the other vaulters have been training for months.
They is a nominative personal pronoun.
Possessive would be theirs, and as you can see, it doesn't fit.
Objective would be them, and it is also incorrect.
Antecedent just means a pronoun.