Answer: option B., which states ∠ DGB is supplementary to ∠ CGB.
Explanation:
The question is incomplete.
Herewith, I attach the image with the diagram and the full question.
1) In the diagram you find that the ∠ DGB and ∠ CGB lie in the same plane and they form a straight ray.
2) That proves that they add up 180°.
2) The definition of supplementary angles is that they add up 180°. Then, it has been proved that they are supplementary angles.
3) Hence the answer is the option B. which states ∠ DGB is supplementary to ∠ CGB.