1.1, 1.2, 1.3, 1.4,............. are called decimal numbers and not just numbers. Integers are numbers which are both +ve an -ve like -2,-1,0,1,2......... . 0 is neither +ve nor -ve number.
When the problem statement uses just the word "numbers",
you can consider both integers as well as decimal numbers. You can not assume the either way. You can consider integers only when the word "integer" is explicitly used in the problem statement. Here, in this problem the word "integer" is not used. So it could be either integer or decimal numbers. I agree that answer is D but only if we assume the numbers to be integers. So I just think that the problme statement should have used the word "integers".