1. If the problem is asking "which statement is true", the list of options to choose from must follow, but it is not a case with this post. 2. I perfectly understand that the expected answer is "the lines remain parallel", but the problem MUST say that the rotation 90 degrees is about the common center. Otherwise, it may happen that the two parallel lines will become coincide.
Hi One example of parallel Lines purple and green rotating 90° and moving to the right:Wish You the Best in your Studies.