Question

Which sentence has an adjective clause?
Mike rode his bike on mountain trails because he found them challenging.
Gary donated to charity whenever he could.
Liz, who could always make people laugh, was loved by the whole block.
Ever since Adam was a little boy, he had helped his father in the fields.

Answer 1

The answer is:
Liz, who could always make people laugh, was loved by thw whole block. 

An adjective clause has a formula: relative pronoun or adverb + subject + verb 

The relative pronoun here is "who"
subject= people
verb= laugh

Other relative pronouns are: whom, whose, that, which. For adverbs: when, where, why.

It also answers: What kind of person is Liz? This fufills its function as an adjective. Other functions of an adjective answers: Which one? How many?