题目选项分析

Consumer advocate: Ephedra is a naturally occurring compound that some people use as a weight-loss aid. Recently, the government prohibited the sale of dietary supplements containing ephedra on the grounds that ephedra has been shown to have grave side effects. This prohibition is unreasonable. Echinacea is another natural compound that has been shown to have side effects, yet echinacea is widely available at health food stores.

The consumer advocate's argument depends on which of the following assumptions?

【选项】Before the prohibition, ephedra had been available in health food stores.