General Idea:
Pythagorean theorem states that in a right triangle, if side of triangle is given by ' a ', bottom of the triangle is given by ' b ' and hypotenuse of triangle is given by ' c', then Sum of squares of a and b is equal to the square of hypotenuse.

Applying the Concept:

Conclusion:
The length of the missing side of the right triangle, when side 8 & bottom 15 is 17. The correct answer is option B!!