Question

where is the most common place to put a tag which identifies an animal?
skin
nares
vibrissae
auricle

Explanation:

The auricle (ear) is a common place for animal - identification tags. It is easily accessible and visible. Tags on the skin may fall off or cause skin problems, nares (nostrils) and vibrissae (whiskers) are not practical locations for tagging.

Answer:

Auricle