To determine if 3 side lengths are a triangle, use the triangle inequality theorem, which states that the sum of 2 sides of a triangle must be greater than the third side.
Therefore, all you have to do is add together each combination of 2 sides to see if it's greater than the third side.
Let's check the given choices:
A.) 8, 12, 16
8 + 12 > 16
18 > 16 ✔
8 + 16 > 12
24 > 12 ✔