Here's why:

* Conjugate acid-base pairs differ by a single proton (H+).

* NaOH (sodium hydroxide) is a strong base because it readily donates a hydroxide ion (OH-) in solution.

* When NaOH donates an OH-, it leaves behind a sodium ion (Na+).

* The OH- then combines with a proton (H+) from the solution to form water (H₂O).

Therefore, the conjugate acid of NaOH is H₂O.