What does ¿cómo estás? mean a. what are you doing? b. where are you? c. how are you? d. where do you live?

It means C "how are you"

¿Cómo estás? mean

C. How are you

That is because Cómo means how and estás means are you, since estar conjugated to Tú (you) is estás

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.