It is a. A right triangle is proven to be a right triangle with its right angle. Line a and c forms the right angle. C and b are much longer than a, so it is fair to assume that their measurements are a bigger number. It can’t be b, because b + c < a doesn’t make sense as a is the smallest side and b and c are longer. C doesn’t make sense, as side b is longer than c. D doesn’t make sense as the triangle theorem states that the sum of two sides has to be greater than the longest side for it to be a triangle. This is obviously a triangle. So your final answer is a.
