The sequence increases by 3 each time. Its nth term is 4 + (n − 1)×3 = 3n + 1, so the 10th term is 31. An arithmetic sequence changes by the same amount each step. Use aₙ = a₁ + (n − 1)d, where a₁ is the first term, d is the common difference, and n is the term number. Do not multiply the common difference by n directly; there are only n − 1 jumps from the first term to the nth term. The correct choices are The nth term is 3n + 1, The common difference is 3, The 10th term is 31, because each of these satisfies the required condition.