Concept:The sentence needs the set phrase “as best I can,” meaning “to the best of my ability.”Explanation:The phrase “as best I can” is the correct idiomatic form after “as.”We say: “I’ll try to convince him as best I can.”Option B gives “as best as I can,” which is not the standard expression in formal English.Options C and D do not fit the structure of this idiom.Answer:A. best