The sex of prawn can be externally identified by:

Correct option is A

Correct Answer: (a) II chelate legs
Explanation:
→ In many prawns (including Macrobrachium spp.), males possess enlarged second pereiopods (second chelate legs) (large claws) used in mating displays and dominance — a reliable external sex indicator.
→ Females lack the pronounced enlargement seen in mature males.
Information Booster:
→ Other sexual characters (appendix masculina on pleopods) are also diagnostic but the enlarged second chela is an easy field marker for males.
Additional Information (Other Options):
(b),(c),(d): Not the standard external features used to differentiate sexes in M. rosenbergii.