In understanding the concept of anchoring, which two factors play an essential role?

A) Price and quantity of equilibrium
B) Income and preferences
C) Utility maximization and the budget constraint
D) The context and the information available

Anchoring refers to the cognitive bias where people rely too much on the first piece of information they receive (the anchor) when making subsequent judgments or decisions. The two essential factors that play a role in anchoring are the context in which the information is presented and the information available. These factors influence the anchor that people use and can lead to biases in their subsequent decision-making processes. Therefore, option D is the correct answer. Option A (Price and quantity of equilibrium) and option C (Utility maximization and the budget constraint) are not directly related to the concept of anchoring, while option B (Income and preferences) is only tangentially related.