What equipment for fog signals is required for a vessel 20 meters in length?

For a vessel that is 20 meters in length, the required equipment for fog signals includes a whistle and a bell. Under the Navigation Rules, specifically regarding sound signals in restricted visibility, vessels of this size must be able to produce certain sounds to ensure safe navigation.

The whistle provides the necessary sound signal to communicate the presence of the vessel, while the bell serves as an additional means to signal, particularly for vessels at anchor. The combination of these two signals complies with the regulatory requirements, enabling other vessels to be aware of the vessel's presence and position in foggy conditions.

The other options would not fully meet the requirements set forth for vessels of this length in terms of fog signaling, as they either include equipment not required or omit essential components for sound signaling. Understanding the specific requirements for different vessel lengths and their corresponding fog signal obligations is crucial for ensuring safety on the water.