The Following Figure Shows Equilibrium at the Industry and Firm

The following figure shows equilibrium at the industry and firm level. Figure 9.6 In the figure,
S₁, S₂, S₃ are the market supply curves.
D₁ and D₂ are the market demand curves.
MC is the marginal cost curve of the firm.
MR₁ and MR₂ are the marginal revenue curves of the firm.
ATC is the average-total-cost curve of the firm.
According to Figure 9.6, a shift of the S curves in the graph on the left side represents:

A) an increased supply because the firm produces more.
B) an increased supply because more firms are producing.
C) an increased supply resulting from a larger number of customers.
D) an increased supply resulting from a lower demand.
E) an increased supply resulting from a lower price.