Students in a biology class studied the effects of temperature on the production of carbon dioxide by yeast cells. They designed an investigation using materials similar to those shown below. They counted the number of carbon dioxide bubbles produced by the yeast at different temperatures. The graph below shows the results.

 
Which of these corresponds to the amount of carbon dioxide that would most likely be produced at 30°C?
F   20 bubbles per minute
G   40 bubbles per minute
H   60 bubbles per minute
J   80 bubbles per minute