Option 1: Megasthenes : Indica - This pair is properly matched. Megasthenes was a Greek ambassador to the court of Chandragupta Maurya in ancient India and he wrote a book called "Indica" which provided valuable information about Mauryan empire.

Option 2: Ashvaghosa : Buddhacharita - This pair is properly matched. Ashvaghosa was an Indian philosopher and poet who wrote the Buddhacharita, an epic poem about the life of Gautama Buddha.

Option 3: Panini : Mahabhashya - This pair is not properly matched. Panini was an ancient Indian grammarian who composed the Ashtadhyayi, a grammar text of the Sanskrit language. Mahabhashya, on the other hand, was a commentary written by Patanjali on Panini`s work.

Option 4: Vishakhadatta : Mudra-rakshasa - This pair is properly matched. Vishakhadatta was an ancient Indian playwright who wrote the play Mudra-rakshasa, which is a political drama set in the times of the Mauryan empire.

So, the correct answer is option 3, where Panini is incorrectly paired with Mahab