At night, you see a vessel ahead displaying only sidelights and a sternlight, with no masthead light or all-round white light visible. What does the absence of a masthead/all-round light suggest?

1. The vessel is likely a sailing vessel under sail alone (no engine running)
2. The vessel is a large commercial ship
3. The vessel is at anchor
4. The vessel's lights are faulty and it should be reported immediately