When a sample of rust was mixed with acid, the rust changed into two simpler substances: W and Z. The substances W and Z could not be broken down into simpler substances. A. The substances W and Z are compounds. B. Rust is a compound made of two elements. C. The substances W and Z are not made of atoms. D. Rust is an element that breaks into compounds.

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.

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