Question

Which number produces a rational number when added to 0.25? ​

Answer 1

The answer is 2/9 or A

Answer 2

The step of adding it to 0.25 (or 25/100, or 1/4) is indeed not relevant. 0.25 is rational.

A rational number added to a rational number gives a rational number. A rational added to an irrational number doesn't.

so effectively the task can be reduced to "wich one of these is a rational number?"

And that's only true for A. 2/9

All others can't be represented as a discrete/finite fraction / ratio.