Self-study
Support On Earth, biological activity leads to a change in the ratio of isotope S-34 to isotope S-32. ████████ █ █████ ██████████ █████████ ██ ███████ ██████ ████████ ██████ ██ █████ ████████ █████ ████ ██ ███████████ ████████ ██████ ████ ██████ ███ █████████ ██ ████ ██ ██████ ██████████ ██ ██ ████████ ████ ████ ████████ ██ █████
Summarize Argument
The author concludes that life is unlikely to have occurred on Mars. This is because on Earth, biological activity leads to a change in the ratio of S-34 to S-32. But in a meteorite from Mars, we only see ratios of S-34 to S-32 that we see in Earth rocks dating from before life on Earth.
Notable Assumptions
The author assumes that life on Mars would lead to a similar change in S-34 to S-32 ratio as observed on Earth. The author also assumes that the ratio in the Martian meteorite is representative of Mars generally. In addition, the author assumes that the Martian meteorite did not leave Mars before life could have arisen on Mars.
23.
Each of the following, if █████ █████ ██████ ███ ████████ ███████
a
Life forms that ████ █ █████████ ██████ ██ ███ █████ ██ ████ ██ ████ ████ ████ ██ ████ █████ ██ █████ █████ ████ ███████ ██████████
This raises the possibility that life on Mars would lead to an S-34 to S-32 ratio that isn’t the same as what we observe on Earth.
b
The effects of ████ ██ ███ █████ ██ ████ ██ ████ ██████ ██ █ ██████ ██ ████████ ███ █████████████ ███████ ████ ██████ ██ █████ █████ ███ ████ ███████
This raises the possibility that life on Mars would lead to an S-34 to S-32 ratio that isn’t the same as what we observe on Earth.
c
The ratio of ████ ██ ████ ██ ███ █████████ ██ ███ ████ ██ ████ ██ ████ ██ █ █████ ██ ███ ████ ████ ███ ████████ ██ ███ █████████ ████ █████
This strengthens the argument by making the Martian meteorite representative of Mars rock as a whole with respect to the S-34 to S-32 ratio.
Directionally wrong
Directionally wrong
Answers that, if they have any effect, do the opposite of what we want (weaken when we're trying to strengthen, or strengthen when we're trying to weaken).
d
Relatively few terrestrial ███████ ███████ ███████ ████ ███ ████ ██ ███ █████ ████ █████████ ███ ████████ ██ ██████████ █████████
This points out that even many Earth rocks don’t have a ratio that reflects life. This raises the possibility that the Martian meteorite, even if it doesn’t have ratio that reflects life, doesn’t rule out the possibility of life on Mars.
e
The current ratio ██ ████ ██ ████ ██ ████ ██ █████████ ████ ████ ██ ███ ████ ███ ████████ ██ ███ █████████ ████ █████
This raises the possibility that life might have arisen after the meteorite left Mars. Perhaps the ratio of S-34 to S-32 on Mars today does reflect life, even if the meteorite we discovered does not have that ratio.