Which plants are considered contact poisons?

Contact poisons refer to plants that can cause irritation, rashes, or other allergic reactions upon direct contact with skin. In the context of this question, poison ivy, poison oak, and poison sumac are well-documented as plants that produce urushiol, an oily resin that triggers allergic reactions in many individuals.

When a person comes into contact with any part of these plants, the urushiol can bind to the skin, leading to symptoms such as itching, redness, and blisters. This is why they are classified as contact poisons; even a small amount can lead to discomfort and significant skin reactions.

Other options either include plants that do not produce the same allergenic response or contain fictional names, which do not refer to recognized plants that cause skin irritation. Therefore, the correct answer identifies the trio of plants commonly known to cause contact dermatitis, making it the best choice among the options presented.