Which of the following is parallel to -axis?

**(A)**

**(B)**

**(C)**

**(D)** Both **(A)** and **(C)**

**(E)** None of the above

Any equation of the form is parallel to -axis and equation of the form is parallel to -axis where a is any real number.

Therefore, is parallel to -axis because it can be written as .

and are parallel to -axis because they can be written as and respectively. We can show these equations on the graph as following:

Hence, the answer is **(D)**.