Which of the following is the measure of  ðqrs?                 a.  80°      b.  115°      c.  90°      d.  100°

That's a "right angle", measuring 90 degrees.

How we know this:
The only thing in the picture that tells us is the little square
drawn in the corner by ' R '.  That's the symbol that's used
on a drawing to show that an angle is 90 degrees. 

Without that little square, there's nothing else in the picture
to tell us the measurement of that angle.

The answer is 109 times per second