Final answer:
A 'special circumstance' under maritime regulations usually refers to an atypical situation requiring deviation from standard navigation rules. Neither 'Speed in fog' nor 'Two vessels crossing' are special circumstances as they are covered by the rules. 'More than 2 vessels meeting' may qualify as a special circumstance if the situation isn't adequately addressed by the rules.
Step-by-step explanation:
The question seems to be related to the interpretation of the International Regulations for Preventing Collisions at Sea (COLREGs), which could be discussed in a high school level physics or maritime safety course. Under COLREGs, a "special circumstance" could be any situation that is not strictly covered by the existing rules, or that requires deviation from those rules to ensure safety. In the examples provided:
- More than 2 vessels meeting might be considered a special circumstance if the meeting cannot be covered by the rules for two-vessel encounters.
- Speed in fog typically refers to maintaining a safe speed under Rule 19 (Conduct of vessels in restricted visibility), which is a requirement rather than a special circumstance.
- Two vessels crossing is a standard situation covered under Rule 15 (Crossing situations).
- A vessel at anchor is addressed under Rule 30 (Anchored vessels and vessels aground) and is not a special circumstance.
In context of maritime safety and the COLREGs, a special circumstance would generally refer to an atypical or unforeseen situation requiring actions outside standard rules to maintain safety. The assessment of what constitutes a special circumstance is typically left to the discretion of the vessel's captain or pilot.