Since the graph is a straight line, it is a linear function. For a non - linear function the graph is a curved one.
Every function is also a relation as it can be expressed as a set of ordered pairs. But the opposite of this is not true. Not every relation is a function. To test if a relation is a function we use the vertical line test. A vertical line crosses a function only once at a given value of x.
Therefore, the answer to the given question is option D. Linear Function and a Relation