Is it
which of the following materials contains components in a fixed ratio?
a.
element
b.
compound
c.
mixture
d.
solution

B. compound

Explanation: "A compound is a substance made up of two or more elements that can only be separated by chemical means. The elements that make up the compound are always resent in the same ratio."

"A mixture does not have a fixed ratio. The components of a mixture keep their unique properties and identities. They can be separated physically."

I know this is late but maybe it will help someone else in the future.

it's filtration, but this is an assumption so my apologies if i got this