Please help me with these questions.

Theorem: The sum of two odd integers is even. Proof: Let m and n be any two arbitrary odd integers: 1. m = 2k1 + 1, for some integer k1 2. n = 2k2 + 1, for some integer K2 3. m + n= (2k1 + 1) + (2/2+ 1) 4. m + n = 2 (k1 + k2), where k1 + k2 is some integer 5. m + n is even In the proof shown above, what is the correct justification in the fourth step for the claim that m + n = 2(k, + kz)? O Algebra and definition of even integers Definition of odd integers Definition of even integers Integers are closed under addition Which of the following is how every proof by weak induction must begin? Suppose P(n) is true, we must show that P(n+1) is true O Suppose P(k) is true for all k n