Remember that
The Triangle Inequality Theorem states that the sum of any two sides of a triangle must be greater than the measure of the third side
You only need to see that the two smaller sides are greater than the largest side
Verify each option
Applying the triangle inequality theorem
A 3 ft. 4 ft. 5 ft
3+4 > 5 ----> is true
that means ----> the three sides form a triangle
B. 5 cm, 8 cm, 15 cm
5+8 > 15 ----> is not true
that means -----> the three sides do not form a triangle
C. 7 in, 7 in, 7 in
7+7 > 7 ----> is true
that means ----> the three sides form a triangle
D. 10 m, 10 m, 15 m
10+10> 15 ----> is true
that means ----> the three sides form a triangle
therefore
The answer is option B