Solution:
The zeros of a polynomial function are the points at which the graph of the function cuts the x-axis.
Given the graph of the polynomial function as shown below:
[tex]\begin{gathered} When\text{ the curve cuts the x-axis twice, this implies that the graph has 2 zeros.} \\ When\text{ the curve cuts the x-axis once, this implies that the graph has only 1 zero.} \\ \end{gathered}[/tex]Since the curve on the graph cuts the x-axis once, it implies that the graph has one zero.
The correct option is D.