The Supply Curve for IPhones Is Upward-Sloping Because

Multiple Choice

The supply curve for iPhones is upward-sloping because

A) when the price of an iPhone rises, it must be due to increased costs in producing iPhones, so producers must charge more.
B) a higher iPhone price gives shoe producers incentive to produce more iPhones.
C) iPhones are produced by only a few producers.
D) iPhone producers always want to satisfy the demand for iPhones by consumers.
E) as the price of an iPhone rises, per-unit costs of production fall.