lsat-24-20

Questions 20-21 Some people have been promoting a new herbal mixture as a remedy for the common cold. The mixture contains, among other things, extracts of the plants purple cone-flower and goldenseal. A cold sufferer, skeptical of the claim that the mixture is an effective cold remedy, argued, "Suppose that the mixture were an effective cold remedy. Since most people with colds wish to recover quickly, it follows that almost everybody with a cold would be using it.    Therefore, since there are many people who have colds but do not use the mixture, it is obviously not effective."

20. Each of the following is an assumption required by the skeptical cold sufferer's argument EXCEPT: (A) Enough of the mixture is produced to provide the required doses to almost everybody with a cold. (B) The mixture does not have side effects severe enough to make many people who have colds avoid using it. (C) The mixture is powerful enough to prevent almost everybody who uses it from contracting any further colds. (D) The mixture is widely enough known that almost everybody with a cold is aware of it. (E) There are no effective cold remedies available that many people who have colds prefer to the mixture.

这道题我看不懂以上粗体彩色部分，这两句话是矛盾的吧？？？ 答案是c