Braincells = lost can someone fill in the blank

The 8 perpendicular pairs of lines are:

I started with AB and worked counterclockwise around the figure so that I could methodically list each pair of perpendicular lines. Perpendicular lines always form a 90 degree angle. While the square angle markers aren't there, I'm assuming your teacher meant to put them in.

Alternatively, you can count the number of right angles and you'll also get 8 as the answer.