Final answer:
The function that represents a direct variation is a. (f(x) = 2x).
Step-by-step explanation:
The function that represents a direct variation is a. (f(x) = 2x).
In a direct variation, the output (y) is directly proportional to the input (x), and the equation takes the form y = kx, where k is a constant. In this case, the constant k is 2, so the function is f(x) = 2x.