Final answer:
The best course of action is to throw away the art supplies without clear labels and an AP seal, as they are potentially hazardous for children's use.
Step-by-step explanation:
When receiving art supplies with unmarked jars or plastic containers, it is important to prioritize the safety of the children. Option 3, throwing away the materials, is the best course of action as the materials lack clear labels and the AP seal, indicating they are not safe for children's use. Even older children should not be exposed to potentially hazardous art supplies. It is crucial to maintain a safe environment by properly disposing of these materials.