Answer: D. The system of equations does not have only one solution because the lines do not intersect at only one point.
Step-by-step explanation
The wording your teacher went with is a bit awkward (in my opinion).
It should be more along the lines of "The system of equations has infinitely many solutions since the lines intersect infinitely many times"
This is because one line perfectly overlaps the other. So a solution is any point (x,y) that's on the line. We consider this system to be consistent and dependent.