Which of the given species have been extinct now?
i- Dodo
ii- Stellar's Sea Cow
iii- Red Panda
iv- Pigmy Hog
v- Quagga

i,ii and v

The IUCN Red List is recognized as the most authoritative guide to the status of biological diversity.

The IUCN Red List is set upon precise criteria to evaluate the extinction risk of thousands of species and subspecies. These criteria are relevant to all species and all regions of the world. The aim is to convey the urgency of conservation issues to the public and policy makers, as well as help the international community to try to reduce species extinction. 

Dodo, Stellar's Sea Cow and Quagga are extinct species. Red Panda is an endangered species. Pigmy Hog is critically endangered.