TASK DEFINITION: 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.
PROBLEM: Question: When in the stratosphere, Dean can tell that the temperature is getting cooler as the altitude he is at 
 Option1: increases 
 Option2: decreases 
 Explanation: The stratosphere contains the ozone layer, the temperatures increase as altitude increases.

SOLUTION: decreases

PROBLEM: Question: Jeff found some very dense water. He knows it is dense because it takes up _____ space than less dense water. 
 Option1: more 
 Option2: less 
 Explanation: More dense water takes up less space than less dense water.

SOLUTION: less

PROBLEM: Question: Eric measures 20 hydrogen ions per 100ml in one solution. Another solution has 30 hydrogen ions per 100ml. The solution with more hydrogen ions is _____ acidic. 
 Option1: more 
 Option2: less 
 Explanation: With a higher concentration of hydrogen ions, a solution is more acidic but has a lower pH.

SOLUTION:
more