Answer:
The correct option is C. 101°
Step-by-step explanation:
For better explanation of the answer see the attached figure :
Since, Angle formed at the center is equal to the angle measure of its opposite arc
⇒ ∠AOD = 91°
Also, The angle formed in the segment is half the angle formed at the center of the circle
⇒ ∠DOB = 2 × ∠BCD
⇒ ∠DOB = 2 × 100°
⇒ ∠DOB = 200°
Now, ∠DOB = ∠BOD + ∠AOB
⇒ ∠AOB = 200 - 91
⇒ ∠AOB = 101°
Now, Angle formed at the center is equal to the angle measure of its opposite arc
⇒ a = ∠AOB
⇒ a = 101°
Hence, the correct option is C. 101°
