The graph of a linear equation may not be a straight line.

If this is a true false question. The answer is false. The idea behind a linear equation is that it is a straight line. Proof for this is the y=mx+b equation. Where m defines a constant slope(or in other words, a straight line) and b represents how high the line appears.
As you can see there is nothing that could bend the line into a more curvy shape (things that do bend are polynomials and such)