Until 1985 all commercial airlines completely replenished the cabin air in planes in flight once every 30 minutes. S...

Emil-Kunkin on January 19, 2022

Hi Abigail, it is not possible that there are two correct answer choices. In this case, we are told that there was a change in how often air was replaced which leads to two things: higher carbon dioxide and easier illness transmission.

Since we know that the air would be replaced only twice in a two hour flight now, and it would have been replaced four times on that same flight in 1980, we can safely conclude that the carbon dioxide content would be greater on the new flight.

B is trickier. The passage does suggest that airborne illness is easier to spread flying today than it would have been in the 80s, however there are many factors that impact airborne illness transmission. While one factor (air recycling) may have made spread easier, there could be other things, like better filtration, sanitation, and masks, that make it harder for airborne diseases to spread. We have no idea about any of these other factors. B tells that flyers today are more likely to get sick, but the passage says nothing about other factors that might have improved. Therefore we can't conclude that people are more likely to get sick just because one contributor to illness spread has increased.