PLEASE HELP. I CAN'T FIGURE THIS OUT

Answer:
Option C is the right choice - a⊥b, by Perpendicular Transversal Theorem
Step-by-step explanation:
The Perpendicular Transversal Theorem states that in a plane state, if any given line is perpendicular to one of two given parallel lines , then it is perpendicular to the other line also.
So, as per the definition, we can see that 'a' and 'c' are parallel lines and line 'c' is perpendicular to 'b' so. 'a' will also be perpendicular to 'b'.