Which is the correct label of the parallel lines? Parallel lines a and b are shown. Points A and B lie on line a while points C and D lie on line b.

The letters a and b are separated by two vertical lines.
There is a horizontal line with arrows on either end over the letters A A. There is another horizontal line with arrows on either end over the letters C B. A vertical line with a horizontal line intersecting it at the bottom separates the two pairs.
There is a horizontal line over the letter A with one arrow on the right end. There is a horizontal line over the letter B with one arrow on the right end. The letters are separated by two vertical lines.
There is a horizontal line with arrows on either end over the letters A B. There is another horizontal line with arrows on either end over the letters C D. A vertical line with a horizontal line intersecting it at the bottom separates the two pairs.