Explanation:

The word 'क्षमा' (Kshama), meaning forgiveness, is an abstract noun and is generally used in its singular form. It does not typically form a plural 'क्षमाएँ' in standard Hindi grammar. The other pairs ('लता-लताएँ', 'गाथा-गाथाएँ', 'कन्या-कन्याएँ') correctly show singular and plural forms.