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: The air gets thicker when it is 
 Option1: hot 
 Option2: cold 
 Explanation: Increasing air temperature decreases atmospheric pressure.

SOLUTION: cold

PROBLEM: Question: Hassan and Ratna each received new automatic cameras as presents. To test their new cameras, Hassan took a picture of the beach that afternoon, while Ratna waited until it was dark outside to take a picture of a python in the moonlight. The shutter of whose camera stayed open shorter? 
 Option1: Hassan 
 Option2: Ratna 
 Explanation: A camera shutter stays open longer in dim light to let more light in.

SOLUTION: Hassan

PROBLEM: Question: Curt wants to make a drink from chocolate chips and milk. To make the chips melt more slowly, Shane will use chips that are 
 Option1: bigger 
 Option2: smaller 
 Explanation: It would be hard to get a big chunk of chocolate to dissolve in your milk or hot water. Maybe you could make hot chocolate from some smaller pieces like chocolate chips, but it is much easier to add a powder to your milk. This is because the smaller the pieces are, the more surface area they have.

SOLUTION:
bigger