Fact 1: If all members of a species cannot produce offspring then that species will likely become extinct.

Fact 2: Passenger pigeons are extinct.

Given the two facts above, answer the question "What could not produce enough offspring?" with the following options: 
- Deoxyribonucleicacid
 - killer whales
 - Echinoids
 - single-celled organisms
 - sparrows
 - great white sharks
 - passenger pigeons
 - one celled organisms


 

       passenger pigeons  