Write a correct answer to the given question based on its associated fact. Make sure that your answer is contained in the associated fact. Don't be creative and introduce any new word that is not mentioned in the associated fact! Remember that the associated fact has been rearranged to form the question. So, the correct answer words must lie within the associated fact. The correct answer can be a word, phrase, or even a sentence.

Fact: The crystallized rocks are made by lava from the mantle. 
Question: Where does the lava come from that makes igneous rocks?
Mantle.

Fact: living things cannot survive without oxygen. 
Question: what cannot survive without oxygen?
living things.

Fact: Placental mammals house the embryo until it is complete and birth large and mature infants. 
Question: Placental mammals house the embryo until it is complete and birth what?

large and mature infants.