Answer:
A. vertical line: yes.
Explanation:
When we have an equation with only one variable, that means it represents a vertical or horizontal line.
When the equation has the form
, where
is a real number, then it represents a vertical line, because its value is horizontally fixed.
Now, in this case we have the equation

As we said before, this equation represents a vertical line which passes through
.
Therefore, the right answer is A. vertical line: yes.