In the Pythagorean Theorem, whatdoes the "a" stand for?a2 + b2 = c2A. The longest side, or hypotenuse, of a right triangle.B. One of the sides, or legs, that make up the rightangle.C. Any unknown side of a right triangle.

Answer:B. One of the sides, or legs, that make up the right  angle.Step-by-step explanation:The Pythagoras Theorem applies to the right-angled triangles. It is basically a relationship between the sizes of the all lengths of the triangle. The Pythagoras Theorem is given by:C^2 = A^2 + B^2; where A and B are perpendicular and base respectively, and C is the hypotenuse. It is interesting to note that A can either be the perpendicular or the base of the right angled triangle. Same goes for B; it can be either the perpendicular or the base. Both the perpendicular and the base intersect at 90 degrees. But both cannot be the hypotenuse. Therefore, the variable A in the Pythagoras Theorem is one of the sides, or legs, that make up the right  angle, i.e. Option B is the correct answer!!!