Learning $($RL$)$ agent interacting in an environment may include one or more of these components: Policy, Value function and Model. Identify the correct statements in the context of a RL agent?

A$.$ A policy is the agent$$s behaviour and is a map from state to action.

B$.$ A model is the agent$$s representation of the environment; predicts what it will do next.

C$.$ The environment need not be observable

D$.$ Value function is a prediction of the next state.