What makes up the bedrock under the continents and is made of magma which slowly cooled inside the e

I'm no geologist, but my head is extremely hard.

So far as I can remember, granite is most common under the continents, while basalt is most common under the ocean floor. Glasslike obsidian is likely to be formed as molten sand. All the pumice I am familiar with is formed when molten lava comes in contact with water.

So, I'll go with A

Do some reading so you'll be able to answer the question in class when called upon.

http://sciencewithkids.com/science-facts/facts-about-bedrock.html