hello
to solve this question, we asume it's a right angled triangle and we use pythagorean theorem
pythagorean thorem states that the square of the longest side which is the hypothenus of a triangles is equal to the sum of the square of the two other sides which are the opposite and adjacent
according to pythagorean

now we go through the options
from the first option (3, 4, 5)
the longest side here is 5
let's check if this is true

option 1 is represents a triangle
let's check option 2
(2, 5, 9)
longest side = 9

option 2 does not represents a triangle and it's the right option here