Given the task definition and input, reply with output. You are given a short paragraph, a question and two choices to answer from. Choose the correct answer based on the paragraph and write the answer(not the key).

Paragraph: The stratosphere contains the ozone layer, the temperatures increase as altitude increases.
 Question: If Mona is flying her plane in the stratosphere on a journey and she moves lower in the stratosphere, what happens to the temperatures her plane experiences? 
 Choices: A)they increase 
B)they decrease
they decrease