Simplify. Remove all perfect squares from inside the square roots.
Assume a and b are positive.

40 & 50 in the right corner are the complementary angles as when placed in a sum (added together) they make 90°

The first one, i believe, would be correct. all the others have one thing in common, and that's that they have repeating numbers. in the second one, x and y have repeating 6's and 3's, and in the third, x and y have repeating 6's as well. in the last one, there are repeating 3's. the first one has no repeating numbers.