Which of the following is a characteristic of pyrophoric materials?

Pyrophoric materials are defined by their ability to ignite spontaneously in air, which makes option B the correct choice. This characteristic poses a significant risk during handling and storage, as these substances can catch fire without the need for an external ignition source. Such materials may ignite when exposed to oxygen in the air, often at room temperature or slightly above, depending on their specific properties.

The other options do not accurately reflect the nature of pyrophoric materials. Non-flammability, safe storage without precautions, and a lack of need for special handling are not characteristics of pyrophoric substances. In fact, pyrophoric materials require careful management, specific storage conditions, and often specialized handling procedures to mitigate the risks they pose. Understanding these characteristics helps ensure safety in environments where pyrophoric materials are used or stored.