We have warned them; we have reminded them; we have appealed to their native justice; we have conjured them. which is this?
a.) parallel punctuation.
b.) parallel clauses and sentences.
c.) parallel phrases.

Your answer would be C.

Explanation:

The sentence above contains parallel phrases since the VP pattern auxiliary verb have + participle is repeated in all of them. Parallel structure, also called parallelism, is the repetition of a chosen grammatical form within a sentence. By making each item in your sentence follow the same grammatical pattern, you create a parallel construction.

themselves

an intensive pronoun is a pronoun that ends in self or selves, such as himself, herself, themselves, yourself, ourselves. since band members is a third person plural, the correct intensive pronoun would be themselves. if the band was talked about as a collective noun, itself would be the appropriate intensive pronoun. intensive pronouns are used to add emphasis to the noun it's modifying which is why it directly follows it.