Answer:
(a) Adjective Phrase
Step-by-step explanation:
An adjective phrase is a group of words that describes a noun or pronoun in a sentence. In the sentence above, enjoy describes the state of the person after reading the book- the noun.
An adjective also tells us which noun or pronoun is being talked about. The use of the phrase, "this book", tells us which the specific book the speaker is talking about. We can therefore, conclude that the sentence is an adjective phrase.