Extinction of Steller's sea Cow and passenger pigeon is due to

The correct answer is Option (2) → Over exploitation by human

Option (1) Invasion of alien species — Incorrect. Alien species caused losses such as the cichlid fish in Lake Victoria.

Option (2) Over exploitation by human — Correct. Steller’s sea cow and the passenger pigeon became extinct in the last 500 years through over-exploitation by humans. Over-exploitation is one of the ‘Evil Quartet’, the four major causes of biodiversity loss.

Option (3) Habitat loss and fragmentation — Incorrect. NCERT calls habitat loss and fragmentation the most important cause of extinction in general, as in tropical rain forests. For Steller’s sea cow and the passenger pigeon it names over-exploitation.

Option (4) Co-extinction — Incorrect. Co-extinction is the loss of a species tied to another that goes extinct.

NCERT Extract:
Loss of Biodiversity – “… (ii) Over-exploitation: Humans have always depended on nature for food and shelter, but when ‘need’ turns to ‘greed’, it leads to over-exploitation of natural resources. Many species extinctions in the last 500 years (Steller’s sea cow, passenger pigeon) were due to overexploitation by humans.”