PrepTest 106, Section 1, Question 14
The axis of Earth's daily rotation is tilted(68 more words not shown)
If the statements above are(15 more words not shown)
- AIf Mars had(12 more words not shown)
- BIf Earth's Moon(13 more words not shown)
- CAny planet with(8 more words not shown)
- DGravitational influences other(20 more words not shown)
- ENo planet that(8 more words not shown)
Reading the argument
So the Moon is doing more than simply accompanying Earth. On this account, its gravitational influence keeps Earth's tilt stable enough for a climate that supports life. Remove that support, and we lose the condition the next sentence says life needs.
There are two linked requirements. Earth's stable tilt needs the nearby Moon's influence. A life-supporting climate needs a stable, moderate tilt. Connecting them gives my prediction: without the Moon's stabilizing role, Earth's climate could not support life.
What we’re looking for
We're taking these premises as given. We don't need to explain all the physics of a planet's tilt, and we shouldn't turn a requirement into a promise that a moon guarantees life. The question asks what must follow, so use the chain to see what happens when a required part is missing.
Working the answers
- A
Giving Mars a large moon might address one obstacle, but the passage doesn't say it would address every obstacle. For example, Mars could still lack some other requirement for life. Even granting that the proposed moon stabilized its tilt, a stable tilt is presented as necessary, not as enough by itself to make a planet support life.
- BCorrect
Without its Moon's stabilizing influence, Earth would lose the stable tilt that the passage says can be maintained only through that influence. Without a stable, moderate tilt, its climate would be too extreme and unstable to support life.
This follows through both links. Losing the required Moon means losing the required stability; losing that stability rules out a life-supporting climate under the stated principle.
- C
Having one requirement doesn't guarantee the outcome. The passage says a planet without a stable, moderate tilt cannot support life. It never says every planet with that tilt can support life. Other necessary conditions could still be missing.
- D
Other gravitational influences could affect a planet's tilt without being able to keep Earth's tilt stable in the required way. The passage doesn't measure those other influences or say they have little effect. Requiring the Moon for stability is different from claiming nothing else affects the angle.
- E
Mars has small moons and an unstable tilt. That doesn't establish that every planet with multiple moons is unable to support life. Perhaps a different arrangement of moons could coexist with a stable tilt. The passage gives us no rule disqualifying a planet merely because it has more than one moon.
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