What type of consideration does an agreement to perform an act already required by law represent?

An agreement to perform an act that is already required by law represents insufficient consideration. This is because consideration, in contract law, refers to something of value that is exchanged between parties. For consideration to be deemed sufficient, it must provide some benefit or detriment that was not already required or owed under existing legal obligations.

When one party agrees to do something they are already legally obligated to perform, such as following the law or fulfilling a legal duty, that act does not provide the necessary value to constitute valid consideration. Essentially, since the obligation exists independently of the agreement, it does not enrich the parties or create a new detriment or benefit that justifies the contract. Thus, it is understood as insufficient.

In the context of the provided options, other terms like inadequacy or illegal consideration do not accurately describe the situation where something required by law is offered as consideration, making insufficient consideration the correct terminology.