The acid having most stable conjugate base in aqueous solution among the following is:

Explanation

The correct answer is HI. In aqueous solution, HI dissociates to generate the iodide ion (I-), which is highly stable due to its large size and the ability to distribute its negative charge effectively. This makes the conjugate base of HI very stable. On the other hand, HNO3 forms the nitrate ion (NO3-), which, while stable due to resonance, is less stable than iodide. H2SO4 results in the bisulfate ion (HSO4-), which has partial charge delocalization but is less stable than iodide. HCN forms the cyanide ion (CN-), which is smaller and less stable as a conjugate base compared to iodide.