Butter goes rancid if we keep it outside the fridge.

Salted butter does not need to be stored in the fridge since the risk of bacterial growth is so low. ... However, it will stay fresh longer if it is kept in the refrigerator. Refrigeration slows down the process of oxidation, which will eventually cause butter to go rancid.

I hope this helps!

Most likely a is the answer - because  you generate   38 atp's but also consume an atp.   each atp gives approx. less than 4 kcal so probably a is the closest answer.