b. possessive
Example.
Mushrooms, which come in many varieties, can be expensive.
Adjective
clauses modify the noun or the pronoun in the sentence's main clause.
The first thing to do is to identify the two clauses in the sentence.
First clause: Those may enter the park (the main clause)
Second clause: whose tickets have been punched (the subordinate clause)
Since
adjective clauses generally start with a relative pronoun, it is clear
that the second clause is the adjective clause. The relative pronoun is
"which". Another clue is that adjective clauses are always the
subordinate clause. It modifies the pronoun those.