You are given a question or fill-in-the-blank question, two answer options (Option1 and Option2) and an Explanation. Your task is to find the correct answer (return the string of the correct option, not option1/2) for the given question from the given options and using explanation.

Q: Question: Clare stopped rubbing two sticks together. The sticks became 
 Option1: hot 
 Option2: cold 
 Explanation: Friction causes the molecules on rubbing surfaces to move faster, so they have more heat energy.

A: cold
****
Q: Question: After Sarah finishes her run, she notices that her blood is really pumping. Sarah can know that since it's a hot day, she's giving off what kind of heat compared to usual? 
 Option1: more 
 Option2: less 
 Explanation: On a hot day, an endotherm may give off more heat by increasing blood flow to the surface of the body.

A: more
****
Q: Question: If Jim lowers carbon dioxide to the ocean, the level of acidity in the ocean becomes 
 Option1: greater 
 Option2: smaller 
 Explanation: With higher levels of dissolved carbon dioxide in ocean water, the water becomes more acidic.

A:
smaller
****