If two consecutive terms in an arithmetic progression are 12 and 17, what is d?

Correct answer: 5

The defining rule for an arithmetic progression is d = a next term − a preceding term. Since the consecutive terms are 12 followed by 17, calculate d = 17 − 12 = 5. Thus option C is correct. The order matters: subtracting the earlier term from the later term gives the forward common difference. Option A is the sum 12 + 17, not the difference; option B is merely the first supplied term; and option D is the second supplied term. Because the terms are consecutive, no formula for the sum or nth term is needed. The same difference would continue in the progression, so the next term after 17 would be 22.