The correct option is D Monarch butterfly
Aposematism is a set of warning signals that organisms display to warn predators. This type of warning signals is useful for both prey and predator. This may be in the form of bright colour, odour, sound or any other predictable forms.
Examples: granular poison frog and monarch butterfly show bright colour while skunk produces a bad smell to exhibit aposematism.
Red milk snake cannot exhibit aposematism. It can only mimic to protect from its prey.