In Rana tigrina , which of the following external morphological features is exclusively present in males and helps in distinguishing them from females?

Step-by-step solution

In Rana tigrina (Indian bullfrog), male frogs can be distinguished from female frogs by the presence of sound producing vocal sacs and a copulatory pad on the first digit of the forelimbs. Membranous tympanum, webbed digits in the hind limbs, and nictitating membrane are present in both male and female frogs. Answer: Sound producing vocal sacs