Whick set of the following numbers could be the side lengths of a right triangle? a. 3,4,and 7b. 9,40, and 42c. 8,15, and 16d. 20,21, and 29

If you are familiar with certain Pythagorean triples and other triangle relationships, you can eliminate the first three possibilities easily.
  A. You know that 3, 4, 5 is a right triangle, so 3, 4, 7 cannot be
  B. You know that 9, 40, 41 is a right triangle, so 9, 40, 42 cannot be
  C. You know that 8, 8√3, 16 is a right triangle, so 8, 15, 16 cannot be
  D. 20² +21² = 400 +441 = 841 = 29²

The appropriate choice is ...
  D. 20, 21, and 29

Ithink it’s b, hope this .