Final answer:
An increase in quantity supplied is depicted by a shift from S1 to S2.
Step-by-step explanation:
The correct answer is B. A shift from S1 to S2 represents an increase in quantity supplied. In the diagram, the movement from point y to point x represents an increase in price, which would result in a decrease in quantity supplied. Similarly, a shift from S2 to S1 would represent a decrease in quantity supplied. Therefore, option B, a shift from S1 to S2, is the correct choice.