Which of the following is not classified as dangerous goods?

Answer: C — Biohazardous substances

Biohazardous substances are often not classified as dangerous goods within the traditional framework of hazardous materials, especially in transportation. The classification of dangerous goods typically focuses on items that present a risk of fire, explosion, or toxicity in a conventional sense. Flammable liquids, toxic substances, and explosive materials all share characteristics that pose immediate physical risks during transport. For instance, flammable liquids can ignite easily and cause fires, toxic substances can harm human health and the environment through exposure or leaks, and explosive materials can result in catastrophic incidents if not handled properly. Biohazardous substances, while they can be hazardous in terms of health, are usually regulated under different guidelines related to bio-safety rather than standard dangerous goods regulations. This distinction is crucial in ensuring the appropriate handling and transport protocols are followed, emphasizing the context of public health and safety rather than standard physical dangers.