What principle is violated if total benefit continues to increase but marginal benefit decreases?

The principle that is violated when total benefit continues to increase while marginal benefit decreases relates to the concept of diminishing returns. As one consumes more of a good or service, the additional satisfaction or benefit obtained from each additional unit typically decreases. This is known as diminishing marginal utility. If total benefits are still rising while marginal benefits are declining, it indicates that although you're gaining more in total, the additional benefit from each extra unit consumed isn't as significant, suggesting that the consumption is not operating under typical expectations of diminishing returns.

This aligns with fundamental economic principles, where rational decision-making involves acknowledging that while total benefits can increase with more consumption, the value gained from each incremental unit diminishes. Consequently, individuals may decide to adjust their consumption based on the declining marginal benefits, reinforcing the notion that maximizing utility often involves balancing total and marginal benefits.

In terms of the other choices: the principle of opportunity cost refers to the value of the next best alternative foregone when a choice is made. The principle of utility generally pertains to the satisfaction gained from consuming goods and services without necessarily linking it to marginal changes. The principle of increasing costs relates to a situation where the cost of producing additional units increases, which does not directly connect with the behavior of benefits stated in the question.