Self-study
Scientist: An orbiting spacecraft detected a short-term spike in sulfur dioxide in Venus’s atmosphere. █████████ ███ █████ ██ █████ ██████ ███████ ██████ ██ █████████ ███████████ ███ █████ ███ ████████ ██ █████████ ████ ████ █████ ██ ████ ████████ █████████ ███ ██ ██████ ███ ████████ ████ ████████ ████████ ██████ ███ █████ ██ ██████ ██ ██████ █████████ ████ ████ ██████████ ██ ██████ ███ █████████ ███████████ ███ █████ ██ ███████ ████ ████████ ██████████ ██ ████████ ████████████
Summarize Argument: Phenomenon-Hypothesis
The author concludes that we should not conclude that volcanic activity caused the short-term spike in sulfur dioxide on Venus. This is based on the fact that no active volcanoes have been identified on Venus, and planetary atmospheres are known to undergo cyclical variations in chemical composition.
Notable Assumptions
The author assumes that inactive volcanoes could not have produced a short-term spike in sulfur dioxide on Venus. The author also assumes that there aren’t any active volcanoes that we haven’t identified on Venus that could have produced the spike. Another assumption is that the cyclical variations in chemical composition could have accounted for the spike in sulfur dioxide.
16.
Which one of the following, ██ █████ ████ ███████ ███ ███████████ █████████
a
Conditions on Venus ████ ██ ████████ ████ ███ ██████████ █████████ █████ █████ ██████ █ ████████ ████████ █████████
This suggests that there might be active volcanoes on Venus that we haven’t identified. If we can’t identify eruptions directly, that raises the possibility that our failure to identify active volcanoes doesn’t guarantee the absence of active volcanoes on Venus.
Alternate explanation
Alternate explanation
Weaken: Introduce or support an alternate explanation for a phenomenon.
Strengthen: Helps to eliminate an alternate explanation for a phenomenon.
b
Evidence suggests that █████ ███ █ ██████████ █████ ██ ██████ ███████ ██ ███████ ██████████ ██ █████ ████████
It’s not clear what a short-term spike 30 years ago has to do with the short-term spike detected recently.
c
Levels of sulfur ███████ ████ ████ ██████ ██ ███████ ██████████ ████ ██ ███████ ██████████ ████ ███ ████ █████
We detected a short-term spike in sulfur dioxide on Venus. Comparative levels of sulfur dioxide on Venus and Earth don’t shed light on the cause of a short-term spike.
d
Traces of the ██████ ███████ ████ ████████ █████████ ██ █████ ███ ██████████ ██ ███ ██████████ █████ █████ ███ █████████ ████ ██████
This suggests that traces of sulfur dioxide can last a long time from volcanoes. But this doesn’t explain a short-term spike in sulfur dioxide. We’re not just trying to explain the presence of sulfur dioxide in the atmosphere; we’re trying to explain a short-term spike.
Failed alternate explanation
Failed alternate explanation
Weaken Qs: Answers that try to introduce an alternate explanation, but fall short, or try to explain a different phenomenon.
Strengthen Qs: Answers that try to eliminate an alternate explanation, but fall short, or try to eliminate an explanation for a different phenomenon.
e
Most instances of ██████ ███████ ██████ ██ ███ ███████ ██████████ ███ ██████ ██ ███ ███████ ██ ██████ ██████
If anything, this might strengthen the author’s argument by suggesting another explanation for the short-term spikes on Venus besides volcanoes.