Here's a problem to solve: Sulfur (S), oxygen (O2), water (H2O), and sodium chloride (NaCl) are all examples of pure substances. Which of the following describes all pure substances?

Among the 4 following options, which is the correct answer?

- 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.
 