Answer:
The correct option is D. Angle A is opposite to the side BC.
Explanation:
In a triangle, the included angle of two sides is opposite to the third side.
From the given figure it is clear that, in triangle ABC,
1. Angle A is opposite to the side BC.
2. Angle B is opposite to the side AC.
3. Angle C is opposite to the side AB.
4. Two angles can not be opposite to each other.
5. Any adjacent side of an angle can not be opposite to that angle.
Angle A is opposite to the side BC. Therefore the correct option is D.