The Following Figure Shows Equilibrium at the Industry and Firm

The following figure shows equilibrium at the industry and firm level. Figure 23.6 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 23.6, an upward shift of the MR curve will result from:

A) a larger demand.
B) more firms in the industry.
C) fewer firms in the industry.
D) a smaller demand.
E) the firm being more efficient.