Answer:
Triangle B
Explanation:
It is possible to determine if a triangle contains a right angle using Pythagoras' theorem . If the squares of the two shorter sides add up to the square of the hypotenuse, the triangle contains a right angle.
so when we look at triangle B if we squared and then added the two shorter sides 3/7 and 4/7 we get 25/49 which is the square of the longer side 5/7
so according to the Pythagoras theorem it's a right angle triangle