Given a scientific question, generate a correct answer to it.

Example Input: In living systems, diffusion of substances into and out of cells is mediated by the what membrane?
Example Output: plasma

Example Input: What are kpa, atm, and mmhg measurement units for?
Example Output: pressure

Example Input: If a machine only changes the direction of a force without changing the ratio of the output/input forces, then what is its associated mechanical advantage?
Example Output:
1