Given a fact, create a question that can be answered using the fact. Construct the question such that it is unambiguous, has a unique answer and the answer can be given using the fact.

[Q]: Fact: the mantle is located just below Earth 's crust
[A]: Much iron is in?


[Q]: Fact: volcanoes are often found under oceans
[A]: the ring of fire is made up of?


[Q]: Fact: a ruler is used for measuring the length of an object
[A]:
With a ruler I can measure?