D. Many
and
A. That
Adjectives describe a noun.
Here is an example of "many" used as an adjective:
Many people came to the party.
"Many" is describing the amount of people (the noun) that came to the party. Generally "many" is used as an adjective for describing the number of the noun.
Pronouns are words that can replace nouns. Common pronouns are they, I, we, us, them, him, her, etc. In some cases "many" can be used as a pronoun. Below I provided an example of "many" as a pronoun:
Many were able to attend the party.
"Many" replaces the noun people.
Here is "that" being used as an adjective:
I want that ice cream!
"That" is describing which "ice cream" you want, therefore it is describing the ice cream.
Here is an example of "that" being used as a pronoun:
I want that!
"That" replaces the noun. Usually this would be used when what "that" is was already mentioned prior to this sentence
Hope this helped!
~Just a girl in love with Shawn Mendes