For this question, we have to use the Pythagorean theory since we're dealing with a right triangle.
a² + b² = c²
We're given the value of the hypotenuse and a leg, therefore we're looking for the value of the other leg.
Now let's plug in the given data into our equation.
2² + b² = 5²
4 + b² = 25
b² = 25 - 4
b² = 21
√b² = √21 = b
The correct answer is B) √21
