According to the material, an oxidizer may be a:

• A. Not a gas
• B. Gas
• C. Liquid
• D. Solid

Answer: (A)

Oxidizers are substances that help a fire by providing oxygen, and they can come in more than one physical form. The material emphasizes that an oxidizer may be not a gas, meaning it can exist as a solid or a liquid as well as a gas. In practice you’ll encounter oxidizers as solids (like many nitrates and chlorates) and liquids (such as hydrogen peroxide), and of course there are gaseous oxidizers too (like oxygen). The important point for safety is not assuming a single phase; handling and storage hazards change with whether the oxidizer is a solid, liquid, or gas. The other options only describe one state, which doesn’t capture that oxidizers aren’t limited to one form.