Answer:
Adjective clause: B. Whose branches had died
Word Modified: C. Tree
Explanation:
An adjective clause is a dependent clause, meaning that it is a group of words that have at least a subject and a verb, but that can not stand on its own because it does not express a complete thought. The function of this clause is to modify nouns.
We can normally identify them because they tend to begin with a relative pronoun (who, whom, whose, that, or which) or a relative adverb (when, where, or why), and they often answer the questions <em>How many? What kind? </em>or<em> Which one?</em>
So, <em>Whose branches had died</em> is the adjective clause because it is dependent, it begins with a relative pronoun that is also the subject: <em>whose</em>, it has a verb: <em>had died</em>, and it modifies the noun <em>The tree</em>. Furthermore, it also answers to the <em>Which one?</em> question: <em>Which three had to be cut down?</em> Answer:<em> The one whose branches had died.</em>