The term "power-driven vessel" refers to any vessel __________.

The term "power-driven vessel" is defined in the context of maritime navigation rules as any vessel that has its propelling machinery in use. This encompasses various types of vessels that rely on engine power for movement, including motorboats, cargo ships, and tugboats, among others. The key aspect of this definition is that it specifies the use of machinery for propulsion, which distinguishes power-driven vessels from those that depend solely on wind or human power.

In this context, options such as being primarily sail-powered, restricted to inland waters, or having a specific gross tonnage do not align with the definition of a power-driven vessel. A vessel classified as primarily sail-powered would fall under a different category entirely. Similarly, limiting the definition to only those that operate in inland waters or assigning a minimum capacity in terms of gross tons does not pertain to what constitutes a power-driven vessel as per maritime regulations. The fundamental criterion is the use of propelling machinery, making option A the correct and comprehensive definition.