**Quote:**

In 1985 a consumer agency concluded that Xylo brand bicycles are safer to ride than are Zenon brand bicycles. The agency based the conclusion on the ratio of the number of rider injuries to the number of riding hours for each brand of bicycle from 1981 through 1984. Yet for identically designed bicycles manufactured since 1985, the number of rider injuries has been twice as great among riders of Xylos as among riders of Zenons. Therefore, the agency's conclusion would have been different for the period since 1985.

Which of the following is an assumption that, if true, supports the claim that the agency's conclusion would have been different for the period since 1985?

From the text above, we know that agency made its conclusion back in 1985 that Xylo brand bicycles are safer than Zenon brand bicycles. The report was based on rider injuries to riding hours ratio of bicycles. However, author tells us that after 1985 Xylo riders got two times higher injuries frequency rates than Zenon riders and for this reason, agency whould have different conclusion for the period after 1985. We need to find an assumption among answer choices which would support this author's claim.

A. For the period since 1985, the number of riding hours for Zenons totaled at least half the number of riding hours for Xylos.

Xylo riders got 2 times more injuries than Zenon riders. In case there were 10 times more Xylo bicycles, it would mean that the ratio of injury/riding hours is still in favor of Xylo bicycles and the conclusion of agency would not change. However, it is written in the option A that riding hours for Zenons was at least half of the riding hours for Xylos. Thus, Zenons could have the same riding hours or even more, but not less than 50% of Xylos riding time. Taking into account that Xylos had 2 times higher frequency of injuries, it would mean that Xylos became less safer than Zenons. CorrectB. Of all the bicycles ridden in the period since 1985, the percentage of Xylos ridden was twice the percentage of Zenons ridden.

Since Xylos were 2 times more in the roads than Zenons, we could assume that they would have more riding hours. However, it is not necessary and Zenons could still be used more than Xylos. Thus, we cannot make conclusion based on this assumption. IncorrectC. Prior to 1985, Zenon owners were more likely than Xylo owners to report the injuries they sustained while riding their bicycles.

Our aim is to find the assumption which would help us to claim that after 1985 the agency's conclusion would change. We are not interested in what happened before 1985. IncorrectD. In 1985 the agency had miscalculated the ratio for Xylos, for Zenons, or for both.

Again, it would be relevant to previous report, and we are interested in what happened after 1985. IncorrectE. Soon after the agency had issued its report, consumer demand for Xylos increased more rapidly than did consumer demand for Zenons.

As in option B, even if we have more Xylos in demand, it does not mean that they have more riding hours. Incorrect