Concept:A vs An depends on the sound that follows the article.Explanation:The error is in part (b) of the sentence.We use "an" before words that begin with a vowel sound, not a consonant sound.In the given sentence, "honest" begins with the vowel sound "o".Therefore, we must replace "a" with "an".The corrected part should read: "and pursue an honest livelihood".All other parts of the sentence are grammatically correct.Answer:(b)