Identify the underlined phrase in the sentence.

To improve his writing skills, the student decided to join the creative writing club.
the answer is infinitive
Why is this answer correct?

The answer is correct because "to join" is an infinitive phrase. An infinitive phrase is a verb phrase that begins with the word "to" followed by a verb (in this case, "join"). In this sentence, "to join" functions as the purpose or objective of the student's decision to improve his writing skills.