(1 point) Suppose you wanted to prove the following statement by mathematical induction: 2+4+6++2n = n(n + 1) for all n 1 What would the first line of a proof by induction be? OA. Let P(n) be the statement, "2+4+6+...+2n = n(n+1)*. B. Let P(n) 2+4+6+2n. C. Suppose P(n) = n(n + 1) for all n 1. D. Assume P(n) is true for all n 1. E. Let P(n) be the statement, 2+4+6++ 2n = n(n + 1) for all n 1'. What would you need to show to establish the base case? OA. Show that P(1) is true, that is, that 2 = 1(1+1) B. Show that P(2) is true, since the sum starts with 2. C. Show that 2+4+6++2n = P(1) D. Show that P(0), P(1), and P(2) are true. E. There is no need to establish a base case since the sum has at least four terms. What is the first line of the inductive case for this proof? OA. Assume P(k) is true for some arbitrary k 1, that is, that 2+4+6++2k = k(k+1) B. Assume P(k) is true for some large k 1, say, that 2+4+6++432 = 216(217). C. Assume P(k) implies P(k + 1) for all k 1. D. Assume P(k) is true for all k 1, that is, that 2+4+6++2k = k(k+1). OE. Assume P(k) and P(k + 1) are both true for an arbitrary k 1, that is, that 2+4+6++2k = k(k+1) and 2+4+6++2k+2k+2 = (k+1)(k+2).