We have to plug in each set into the Pythagorean theorem:
A ) 11² + 12² ? 22²
121 + 144 ? 484
265 < 484 ( obtuse )
B ) 5² + 12² ? 13²
25 + 144 = 169 ( right triangle )
C ) 7² + 8² ? 9²
49 + 64 ? 81
113 > 81 ( acute )
D ) 1 + 5 = 6 ( not a triangle )
Answer : A ) 11, 12, 22
