Answer:
The correct answer is option C.
Explanation:
Products A and B are complements and the price of B decreases. This decrease in the price of good B will lead to an increase in its quantity demanded. This will cause a downward movement on its demand curve.
Since A and B are complements, they are used together. So the demand for good A will increase as well. This will be indicated by a rightward shift in the demand curve of A.