The errors in the same sentence error identification questions are always based on grammar or usage.
Standard written English never uses 2 negative words when one will do the job.
Parallel structure is a fancy way of saying that all the language is in the same form. Usually these tricks appear when a sentence contains a series of actions or prepositions. Ex. Before I could go to the lake with my friends, I had to do my chores, walk the dog, and finishing my homework.
A pronoun is a word that stands in for a noun, which is called its antecedent. Singular pronouns (I, he, she, it) stand for singular nouns and plural pronouns (we, they) stand in for plural nouns.