Which of the following sets of triangles could be the lengths of the sides of a right-angled triangle:

For a right angled triangle, minimum condition to be satisfied is the Pythagoras Theorem which is stated mathematically as below:

(Hypotenuse) ² = (Base) ² + (Perpendicular) ²

So let us try each and every option,

For option A:

26² = 9² + 16²

676 = 81 + 256

676 ≠337

So this option is not correct.

For option C:

3.9² = 3.6² + 1.5²

15.21 = 12.96 + 2.25

15.21 = 15.21

So this option is correct.

For option D:

26² = 7² + 24²

676 = 49 + 574

676 ≠ 623

So this option is not correct.

So the correct answer is C.