Under what circumstances may listings be terminated?

The appropriate answer is rooted in the nature of listings and the conditions under which they can be terminated. Listings can indeed be terminated under circumstances such as death of the agent or the principal, if the principal becomes insane and is no longer competent to uphold the contract, or through mutual agreement where both parties decide to end the listing for any number of reasons.

These reasons are grounded in the legal principles surrounding agency relationships and contractual agreements. Death or insanity directly affects the capability of the parties to fulfill the contract, rendering the listing void. Mutual agreement is also a valid reason for termination, as both parties have the right to negotiate and decide to conclude their relationship on amicable terms.

Other options, while they may contain some plausible conditions for termination, do not accurately encapsulate the most universally accepted circumstances recognized in agency law. Therefore, the combination of death, insanity, and mutual agreement effectively covers the critical grounds for the termination of listings.