Assertion: Carnivory is an evolutionary last resort when nitrogen and phosphorus are limited in an ecosystem.
Reason: Large amount of energy and resources are allocated to carnivorous adaptations.

1. Both assertion and reason are true and the reason is the correct explanation of the assertion.
2. Both assertion and reason are true but the reason is not the correct explanation of the assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.