If you would like to know the least possible pair of integers, you can find this using the following steps:
integer ... n
the sum of two consecutive integers ... n + (n+1) = n + n + 1 = 2 * n + 1
is at least 36 ... >= 36
n + (n+1) >= 36
2 * n + 1 >= 36
2 * n >= 36 - 1
2 * n >= 35 /2
n >= 35/2
n >= 17.5
n = 18: 18 + (18+1) = 18 + 19 = 37 >= 36
The correct result would be C. 18 and 19.