Explanation

@mjenei, Happy to help. We're looking to add an assumption that would help strongly support the conclusion of the salesperson's argument. In looking at the stimulus, the salesperson's conclusion is that an inexpensive handheld vacuum cleaner is likely to be sufficient if your vacuuming needs are limited to cleaning small areas of uncarpeted floors. His support is that most of these vacuums are easy to use and can satisfy all of your needs on wood or tile floors. There's a problem, though. The conclusion is about uncarpeted floors. Who's to say that wood and tile floors are the only types of uncarpeted floors? What about marble floors? In order to strengthen his argument, we need to plug in this hole, either by stating that the vacuums work just as well with other types of uncarpeted floors or that wood and tile are the only other types of floors other than carpet. (A) says, "The only types of floor surfaces that most consumers encounter are carpet, wood, and tile." (A) would help the argument a lot. We know the vacuums are great for wood and tile, and the conclusion is about uncarpeted floors. If these are the only types of floors most consumers encounter, then the salesperson's argument is made stronger, so (A) is the correct answer choice. Hope this helps. Let us know if you have any more questions!

Why could the answer not be C?

Why does the answer choice A. include carpeted floor if the passage is focused on Un-carpeted floor specifically wood and tile?