Question

Holes drilled several kilometers into Earth’s crust provide direct evidence about Earth’s interior in the form of

Answer 1

a.
seismic waves.
b.
rock samples.
c.
liquid iron.
d.
volcanic eruption.

Answer 2

Liquid Iron

Answer 3

lol...The answer is NOT liquid iron!

This is very simple, just think about the question for a minute and then eliminate the answers that do not make sense.

Let's go in order shall we? :o)
a. seismic waves
Drilling holes a few kilometers into the Earth has nothing to do with seismic waves. While yes you may create some small vibrations while drilling, we do not use these vibrations for anything. If we want to learn about the inside of the Earth from seismic waves, we can either study waves created by earthquakes or generate our own seismic waves through explosions or ramming the ground with very heavy specialized machinery that create seismic waves that propagate downward and bounce back to detectors. This has nothing to do with drilling holes so this is NOT the answer. You should learn about P-Waves and S-Waves which are what tell us about the composition "deep" in the Earth.
http://3.bp.blogspot.com/-OyPHzu0wpB8/T0oRQilzizI/AAAAAAAAAEc/Ri_YmUIF3BE/s1600/php6TOwx1shadow_p_s-1.gif

b. rock samples.
Obviously if you drill into the Earth, you can bring back rock samples. This is a valid answer.

c. liquid iron
In order to retrieve liquid iron from drilling holes, you would have to drill down several THOUSAND miles until you reach the outer core where liquid iron churns and creates Earth's magnetic field. We have no technology to physically drill this deep.

d. volcanic eruption
What does drilling holes have to do with volcanic eruptions? Nothing!
This is a dumb choice and makes no sense.

I hope this helps!
:o)