Answer:
-16 (assuming you are allowed both positive and negative numbers)
Explanation:
If you use two negative numbers, the result will be a positive, so the only way to get a number below zero is to use one positive and one negative number.
Here's the only options that provide one negative and one positive number:
1 x -7 = -7
2 x -6 = -12
3 x -5 = -15
4 x -4 = -16
5 x -3 = -15
6 x -2 = -12
7 x -1 = -7
Therefore, -16 is the lowest possible product of two numbers with a difference of 8