B. shining a bright light on the objects and testing for decomposition
In explanation, chemical property is a characteristic of a certain substance came from an outcome due to chemical change or reaction. In the situation above, more specifically toxicity is involved in the chemical property/change. Hence, when the object is tested for decomposition. Like for an example of decomposition simply in metals, rusting. Rusting a process of degeneration of metals. Here it works the same. Toxicity is how much damage did a certain entity do to the object.