Answer:
D. 90
Explanation:
We can see that angle a is formed by two lines that ends in opposite sides of the circle, so the segment form the diameter of the circle. So, the measure of the arc is 180 degrees. Then, by the inscribed angle theorem, the measure of angle a is:
[tex]\begin{gathered} a=\frac{1}{2}(180) \\ a=90 \end{gathered}[/tex]
Therefore, the measure of a is
D. 90
