We have an undefined slope. It means that the line is parallel to the y-axis, that is, the slope could be "defined" as an infinite slope (in rough words).
Therefore, the equation of the line through the point (-2, -3) with an undefined slope is:
x = -2 (option d).
This line is represented as a parallel line to the y-axis (x = -2), and it passes through the point (-2, -3).