The ability of mammals to control their internal body temperatures is a factor in the development of their brains and...

Boram on January 14, 2019

Is (d) the correct answer because the passage talks about brains, chemical reactions, and temperature, but does not talk about development of intelligence?

Ravi on January 15, 2019

@smilde11 and @Boram,

Happy to help!

@Boram, D is the correct answer because it is a necessary premise that
must be true in order for the argument to stand a chance. If D is
false, then the argument falls apart. Let's take a look at why this is
the case:

We're told that mammals being able to control their internal body
temperatures is a factor in the development of brains and
intelligence. This is the conclusion of the argument.

We're then told that the brain is a chemical machine, all chemical
reactions are temperature dependent, and any organism that can control
its body temperature can assure these reactions occur at the proper
temperatures. This is the support for the argument's conclusion.

There's a pretty big gap in the argument—the author is assuming that
controlling temperature has something to do with the development of
brains and intelligence. The correct answer choice will likely pick up
on this big assumption that the argument is making.

Since this is a strengthen with a necessary premise question, we can
use the negation test with the answer choices to help us pick the
right answer.

Answer A is incorrect because if its negation were true, the argument
would not fall apart. Additionally, we don't care about organisms that
are unable to control their body temperatures; the argument strictly
deals with organisms that can control their body temperatures.

Answer B is incorrect because even if mammals aren't the only animals
that have the ability to control their body temperatures, the argument
is not wrecked. This is not a necessary premise.

Answer C is incorrect because if the chemical reactions within the
brain are subject to uncontrolled temperatures and the brain can still
support intelligence, this does not make our argument fall apart.
We're concerned with controlled temperatures, not uncontrolled
temperatures.

Answer D is correct because its negation would make our argument fall
apart. D's negation is that the development of intelligence in mammals
is independent of the chemical reactions in their brains taking place
at the proper temperatures. If D's negation is true, then the argument
is wrecked because there is no connection between the premises of the
argument and its conclusion. D is absolutely necessary for the
argument, so it's our correct answer.

Answer E is incorrect because we do not care about organisms that are
incapable of controlling their body temperatures. Like answer A, with
E, we don't care about organisms that are unable to control their body
temperatures; the argument strictly deals with organisms that can
control their body temperatures.

Does this make sense? Let us know if you have any more questions!