Task: Question Answering
Input (English): Background Paragraph: Active transport occurs when a substance passes through the cell membrane with the help of extra energy. This happens when a substance moves from an area where it is less concentrated to an area where it is more concentrated. This is the opposite of diffusion. The substance moves up, instead of down, the concentration gradient. Like rolling a ball uphill, this requires an input of energy. The energy comes from the molecule named ATP (adenosine triphosphate). The energy allows special transport proteins called pumps to move substances to areas of higher concentration. An example is the sodium-potassium pump. 
Story: Gary is a high school student examining two cells under a microscope for his biology class. In a petri dish, marked Cell X, Gary sees that substances inside the cell are spreading apart from each other making it less concentrated. In the dish marked Cell Y, Gary sees substances coming together and moving into close proximity to one another. 
Question: Which cell is utilizing diffusion?
Output (English): Cell X.