The concept of agency authority is foundational in Virginia insurance law, derived from general agency principles and reflected in Title 38.2, Chapter 18. Express authority is explicitly granted in the agency agreement (e.g., soliciting and binding coverage), per Virginia Code § 38.2-1800 et seq. Implied authority, however, is not written but assumed to be necessary for carrying out express duties—such as scheduling client meetings or collecting initial premiums—unless restricted by the insurer. “Mandated authority” (option B) is not a recognized term in Virginia insurance regulations or study materials. Option C (express authority) is incorrect because it’s explicitly stated, not unwritten. Option D (nonexistent) denies the presence of authority, which contradicts the question’s premise. The Virginia Life, Annuities, and Health Insurance study guide likely highlights implied authority as a key concept for agents’ day-to-day operations, making A the correct answer.