Final answer:
Incendiary devices are classified as physical evidence, which is a form of (A) circumstantial evidence in a legal context.
Step-by-step explanation:
Incendiary devices are tangible items that, when used in a legal context, are classified as physical evidence. This type of evidence is any material item that is presented to the court and can help establish the truth or falsity of an allegation. Physical evidence generally falls into the category of circumstantial evidence.
While it can be very powerful, this evidence indirectly supports a conclusion about a fact in question, as opposed to direct evidence which directly demonstrates a fact. For instance, an incendiary device at a crime scene can strongly imply that a deliberate act of arson has been committed, though on its own, it may not identify the perpetrator without additional context.