Answer:
Graph D
Explanation:

Given f(x) is a exponential function
The graph (a) is a graph of an absolute function because we have V shaped graph
The graph (b) is the graph of a line so it is a graph of a linear function
The graph (c) is a U shaped graph. U shaped graph is a graph of a quadratic function.
The graph (d) is a curve shaped graph. It is a graph of an exponential function.