Answer:
A) 15 < x < 24
Step-by-step explanation:
According to the law of the triangle, we know that the lengths of any two sides of a triangle are more significant than the length of the 3rd side. Here A is the answer because 15 is the length of the first side, and 39 is the length of the third side. So the length of the 2nd side is (39-15) = 24. It means that the length of the 2nd side is included between 15<x<24.