Final answer:
Relative clauses begin with words like 'that,' 'which,' or 'who' and act like adjectives by modifying or describing a noun or pronoun.
Step-by-step explanation:
The correct answer is relative clauses. Relative clauses begin with words like 'that,' 'which,' or 'who' and act like adjectives by modifying or describing a noun or pronoun. For example, in the sentence, 'Janis spent her vacation in Goa, which is on the west coast of the Indian subcontinent,' the relative clause 'which is on the west coast of the Indian subcontinent' modifies or describes the noun 'Goa.'