PrepTest 120, Section 1, Question 12
All known living things are made of the(26 more words not shown)
The conclusion follows logically if(7 more words not shown)
- AWithout the existence(12 more words not shown)
- BThere are not(12 more words not shown)
- CThere can never(11 more words not shown)
- DMany yet-to-be-discovered types(8 more words not shown)
- EAny two living(13 more words not shown)
Reading the argument
Same ingredients, same origin? That's the step I want explained. The passage tells us that all known living things share basic kinds of matter, a carbon basis, and genetic codes. We can accept those similarities without yet knowing how the living things originated. Couldn't the same features have arisen separately?
What we’re looking for
We're asked for an assumption that makes the conclusion follow. Then we need a rule connecting at least one of the shared features with a common origin. For example, if sharing the same basic kinds of matter guarantees the same origin, the first similarity would do the work. We wouldn't need an additional rule for carbon and another for genetic codes. One sufficient connection is enough.
Working the answers
- A
Human life might depend on the existence of other life forms without sharing their origin. Perhaps independently originating human life required materials produced by older life forms. Dependence on other life doesn't establish the common origin of human life and all other known life.
- B
This links genetic codes with being carbon based. Those are two features already listed in the evidence. Tying them together doesn't connect either feature with origin. Life forms could meet both descriptions and still, for all we've been told, have originated separately.
- C
Requiring every living thing to have a genetic code adds a broad claim about life, but no rule about origin. Even if every possible living thing had a code, we would still need to know why that shared feature means a shared source.
- D
Undiscovered life forms aren't what the conclusion is about; the conclusion concerns known life. More importantly, predicting that additional forms will be carbon based still doesn't explain why carbon-based life must have a common origin.
- ECorrect
Any two living things made of the same basic kinds of matter now must have the same origin. The evidence says all known living things share those kinds of matter, so we can apply the rule to human life and each other known form of life. That establishes the shared origin the conclusion claims. The answer doesn't need to repeat every similarity in the passage; it supplies a rule that makes one of them enough.
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