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: Rita added more food to the box. It is now _____ to move. 
 Option1: harder 
 Option2: easier 
 Explanation: The full box is harder to move because it has greater mass and therefore greater inertia.

SOLUTION: harder

PROBLEM: Question: Dan is swimming into shallower water. The water the shallower he goes will be 
 Option1: younger 
 Option2: older 
 Explanation: Deeper aquifers typically contain older 'fossil water.'

SOLUTION: younger

PROBLEM: Question: Ice is more common at the top of mountains because it is 
 Option1: hotter 
 Option2: colder 
 Explanation: Glaciers often form in the mountains because higher altitudes are colder and more likely to have snow that falls and collects.

SOLUTION:
colder