The above illustration shows the molecule used by some cells to temporarily store energy. the molecule is used in almost all energy-requiring reactions in cells. this molecule could be considered the "gas" that powers a cell's "engine." what is the name of this molecule?

It seems that you have missed the necessary details and options for us to answer this question so  I had to look for it. Anyway, based on the given description above, the molecule which is considered the "gas" that powers a cell's "engine" is called the Adenosine Triphosphate or ATP. Hope this helps.