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: Mona is flying in a hot air balloon. As she floats lower in the air the air temperature decreases. What will happen to the air pressure? 
 Option1: increase 
 Option2: decrease 
 Explanation: Increasing air temperature decreases atmospheric pressure.

SOLUTION: increase

PROBLEM: Question: Sandra sees a tiny glacier, and notes that it has smaller tributary glaciers flowing into it, in valleys that are 
 Option1: shallow 
 Option2: deep 
 Explanation: Smaller tributary glaciers, like tributary streams, flow into the main glacier in their own shallower U-shaped valleys.

SOLUTION: deep

PROBLEM: Question: Will is smoking a cigarette. This causes _____ oxygen to be available for diffusion in his lungs, so less oxygen will be absorbed into his blood. 
 Option1: more 
 Option2: less 
 Explanation: Smoking reduces the amount of oxygen available for diffusion at the lungs, so less oxygen gets absorbed and blood is oxygenated to a lesser degree.

SOLUTION:
less