Concept:A geometric sequence has nth term Tn=arn−1, where a is the first term and r is the common ratio.Explanation:First term a=3.Common ratio r=39=3.Substitute into the formula:Tn=3(3)n−1.Using index laws, 3(3)n−1=31+n−1=3n.This matches option B.Answer:3×3n−1 (Option B).