given the following measures of the side of triangles, which is a right triangle?

Answer:
Step-by-step explanation:
Essentially, we can use the pythagorean rule that:
a^2+b^2=c^2
c^2 resembles the hypotenuse, which is almost always the largest number. therefore, we simply have to find two which equal the largest side:
9^2+40^2=41^2
81+1600=1681
1681=1681
Based on this math, A is our right angle!
Hope this helps!