Answer:
a continuous and differentiable function
Step-by-step explanation:
We assume this is a vocabulary question, not one seeking an instance of such a function. The description is of a continuous and differentiable function.
The mean value theorem says there is at least one point in the interval (a, b) where the derivative of a continuous and differentiable function is the same as the average slope between the end points of the interval. The tangent at that point is parallel to the secant line.
