Question: Sulfur (S), oxygen (O2), water (H2O), and sodium chloride (NaCl) are all examples of pure substances. Which of the following describes all pure substances?

  Options: 
 A. A pure substance consists of only one type of element.
 B. A pure substance has a definite chemical composition.
 C. A pure substance cannot be broken down into simpler substances.
 D. A pure substance is normally found as a solid at room temperature. 
Answer: B