Planetary bodies differ from one another in their composition, but most of those in the Solar System have solid surfa...

Ravi May 11, 2019

@kms0121,

Happy to help. It sounds like you're wanting some help on drawing out
inferences. The question we're looking at is a must be true question
type, so we need to piece together the premises to see what we can
figure out.

From this stimulus, we have

no volcanic action - >no renewal

no renewal - >lots of craters

We can link these statements together:

no volcanic action - >no renewal - >lots of craters

the contrapositive is

not lots of craters - >renewal - >volcanic action

We know that Europa (as well as some other cold planetary bodies) have
very few craters.

Using the contrapositive of the conditional chain, we know that Europa
satisfies the sufficient condition (not lots of craters), so we can
conclude that Europa has volcanic activity.

Based on our diagramming, we've arrived at a conclusion about Europa
and other cold bodies. Let's see if our anticipated conclusion is in
the answer choices. It's almost a guarantee that it will because with
must be true questions, one answer choice has support from the
stimulus, and the other four choices do not have support.

(E) says, "Some very cold planetary bodies have cores that generate
enough heat to cause volcanic action."

This is precisely the conclusion we made. We know Europa is cold, and
it has to have volcanic action since it doesn't have very many
craters. This is the correct answer choice.

If you're having trouble on these questions, focus on making sure you
are diagramming when you're able to. For this question, diagramming
the conditional statements makes it much easier to see the inference
we can make.

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

oliviafwiener January 22, 2020

can you explain no volcanic action -----> no renewal? isn't that not how you set up that unless statement?