Their holy book is
called the avesta.

I'm not sure your question.

Explanation:

if you are asking whose Holy book is the Avesta it is the Zoroaster. It "is all that remains of a much larger body of scripture, apparently Zoroaster's transformation of a very ancient tradition."

answer might be "si", would be better if you added answer choices

when the outside temperature is too cold, an endothermic animal can generate heat by shivering. endothermic animals must eat much more often than ectothermic animals since it takes energy to maintain a constant body temperature.