Answer:
B. Rust is a compound made of two elements.
Explanation:
A substance is a form of matter which has a constant composition and distinct properties. Depending on whether they can be separated by chemical means or not, they can be compounds or elements, respectively.
The problem tells us that a sample of rust, after a chemical reaction with acid, is separated into two simpler substances W and Z. Therefore, the rust is a compound.
After obtaining W and Z, these substances can not be broken down into simpler substances. Therefore, these substances are elements.
Rust is a compound made of two elements, iron and oxygen.
