Supposing the temperature of 60 degrees increases twice, it becomes 120 degrees (100% increase) and the bottles increase twice as well to 150 bottles (100% increase).
If there are 120 bottles used, we can calculate the temperature using the above assumption when bottle usage increase to 100% which is 150 bottles.
120 bottles/ 150 bottles = 0.8 or 80%
So, if 100% increase in temperature is defines by 120 degrees, what is 80% of 120 degrees?
Then 120 degrees divided by 0.8 will result to 96 degrees (so the answer is letter D) -- the temperature when 120 bottles were used by athletes.