Turning 21 is the time c. when people should think about their future.
What part of speech is 'when'?
"When" can be used as an adverb, conjunction, pronoun, and noun.
"When" is an adverb when it modifies a verb, adjective, or another adverb
"When" becomes conjunction when it starts a subordinate clause.
"When" becomes a relative pronoun when it provides more information about a person, thing, or situation.
"When" can also function as a noun when it represents a time something occurred.
In this case, "when" functions as a relative pronoun.
Learn more about relative pronouns at https://brainly.com/question/14061272
