Self-study
Until 1985 all commercial airlines completely replenished the cabin air in planes in flight once every 30 minutes. █████ ████ ███ ████ ███ ████ ████ █████ █████ ███ ████ ██████████ █████ ███ ██ ███████████ ██ █ █████ ██ ███████ ███ ██████ ███ █████ ██ ██████ ███████ ██ ████ █████ ███ ███ ██████ ██ ██ ███ ████████ █████████ ██ ██ ███████
Summary
Before 1985, all commercial airlines replaced the cabin air in a plane once every 30 minutes. After 1985, airlines replace the cabin air once every hour. The less frequently cabin air is replaced, the higher the level of carbon dioxide in the cabin air and the easier it is for airborne illnesses to spread.
Strongly Supported Conclusions
Modern airplanes have higher levels of carbon dioxide in the cabin air compared to planes before 1985.
18.
Which one of the following ██ ████ ████████ █████████ ██ ███ ███████████ ██████
a
In 1985 there ███ █ █████████ ██ ███████████ ██████████ █████ ███ ██ ██████████ ███████ ████████
This answer is unsupported. We don’t know from the stimulus what caused commercial airlines to replace the rate of replacement from every 30 minutes to every hour.
b
People who fly █████ ███ ████ ██████ ██ ████████ ████████ █████████ ████ ████ ██████ ███ ████ █████ ██ █████
This answer is unsupported. The stimulus is limited to what is true of commercial airlines. For this answer, you have to assume that people who fly today fly on commercial airlines.
c
Low levels of ██████ ███████ ██ █████ ███ ████ ██ ██████████ ███ ████████ █████████ ██ ███████
This answer is unsupported. “Impossible” is too strong in this answer. We only know from the stimulus that higher levels of carbon dioxide can make it easier for airborne illness to spread.
d
In 1980 the ████ ██ █████ ███ █████ ███ ███ ███████████ ██ ██████████ █████████ ███ ██████████ ██ ███████ ██████████ ████ ███ ███████ ██ ██████ ███████ ████████
This answer is unsupported. We don’t know from the stimulus what the effects of carbon dioxide buildup are.
e
In 1980 the █████ ██ ██████ ███████ ██ ███ █████ ███ ██ █ ████████ ██████████ ███████ ██████ ███ █████ ████ ██ ██ █████ ██ █ ███████ ███████
This answer is strongly supported. Since cabin air would have been replaced every 30 minutes during a flight in 1980, that flight would have lower levels of carbon dioxide compared to a similar modern flight.