Which of the following most logically completes the passage below?

Two years ago, officials in Distropia passed landmark piracy legislation to combat an explosion in distribution of pirated DVDs of newly released movies in the country's major cities. Primarily, the legislation created new controls for preventing the entry of pirated DVDs from the neighboring country of Estonia, the major supplier of pirated DVDs to Distropia. If the plan had been successful, the street price for most piratedDVDs in the country's major cities would not have dropped as it did over the past two years, as long as______________.

A.The street price of some pirated DVDs did not drop during that time period.
B.There was a major decrease in the supply of pirated DVDs during that time period
C.The drop in the street price for most pirated DVDs was not caused solely by a decrease in demand for those DVDs.
D.Domestic production of pirated DVDs did not increase during that time period
E.The street price of some pirated DVDs increased substantially during that time period.

OA: C
What's wrong with options B and D? Can any experts explain?