题目选项分析

Letter to the editor: Proposition Q, a controversial measure on this year's ballot, would prohibit the ownership of handguns within the city's limits. Under the plan, gun owners would have a 90-day grace period to turn in their weapons to authorities. Proponents of the proposition argue that fewer handguns on the streets would lead to less violent crime, making the city safer for all of its citizens. Unfortunately, the ban would actually have the opposite effect. Since only law abiding citizens would honor the ban, armed criminals would not only keep their weapons but would also have the confidence to act with impunity on a population that could no longer defend itself. In the letter to the editor, the two portions in boldface play which of the following roles?

【选项】The first is a pattern of cause and effect that the author believes to be true; the second offers evidence to contradict this pattern