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: For a given medium, sound has a slower speed at lower temperatures.
 Question: If Mary is playing music in her room and the heater starts working, causing the temperature to rise, what happens to the speed of the soundwaves her radio is generating? 
 Choices: A)increases 
B)decreases
increases