The correct answer is "Few in the band have learned all of their music yet". When a verb agrees with its pronoun subject, it needs to sound natural. "Neither" and "either" always agree with a verb in singular form, and "anybody" agrees with a verb in the singular form as well.
Explanation: because A claim is an assertion an author or speaker makes to tell something is true but without providing evidence or proof about it, but it could be true and it has to be argued
