Concept:The verb "avail" in this context must be used with a reflexive pronoun and the preposition "of".
Explanation:The underlined phrase "to avail" is incomplete.
The correct structure is "to avail oneself of".
Here, "oneself" becomes "myself" because the subject is "I".
So the correct phrase is "to avail myself of".
Option (b) provides this exact improvement.
Option (a) "to avail of" is missing the reflexive pronoun.
Option (c) "to avail myself" is missing the preposition "of".
Only option (b) makes the sentence grammatically correct.
Answer:(b) to avail myself of