Letter writer: Illegal drug use is often associated with other violent crimes. Statistics indicate that each time police increase their enforcement of anti-drug laws in the city, the number of violent crimes committed in the city declines as a result. However, eliminating criminal penalties for drug use would almost certainly decrease rather than increase the incidence of violent crime. If drugs were no longer illegal, the price would drop precipitously, and drug users would be less likely to use illegal means to acquire the money necessary to support their drug habits.

In the letter writer's argument, the two portions in boldface play which of the following roles?

(A) The first is support offered by the letter writer for a certain forecast; the second is that forecast.
(B) The first acknowledges an observation that refutes the main position that the letter writer takes; the second is that position.
(C) The first is a direct relationship between two activities that the letter writer predicts will hold in the case at hand; the second offers information that, if true, would support that prediction.
(D) The first is a direct relationship between two activities that the letter writer predicts will not hold in the case at hand; the second offers information that, if true, would support that prediction.
(E) The first is a statement that the letter writer believes is true; the second is presented as a logical inference drawn from the truth of that statement.

OA D. Can someone please explain. I chose B and cannot understand what is wrong with it.
Also, while explaining your answers could please tell me the conclusion of the above stimulus.