<u>b) that once grew on an empty lot in New Jersey</u>
Explanation:
Subordinate clauses are groups of related words having a subject and a verb that does not express a complete thought on their own, and therefore, should always be with another clause in order to make sense. Option B has those characteristics. This clause has a subject which is “ancient forest” (the function of “that” is to refer to that subject) and a verb: “grew,” and if we removed this clause from the sentence, the clause would not make sense because it does not express a complete idea on its own
Furthermore, this clause is an adjective clause because it gives us information about the noun “ancient forest.”
