Statement 1 says, in words, "k is 5 greater than some multiple of of j". If j > 5, then that's just another way of saying "the remainder is 5 when we divide k by j". But we don't know if j > 5, using only Statement 1. If j=2, say, then it's impossible for the remainder to be 5 when we divide by j; in this case the remainder would be 1. So we need Statement 2 (which is clearly insufficient alone), and the answer is C.