What does "reefing" a sail mean, and roughly when might a skipper decide to do it?

A. Reefing means removing a sail completely and stowing it below decks

B. Reefing reduces the effective area of a sail that's exposed to the wind, typically done as wind strength increases, to keep the boat manageable, reduce heel, and reduce strain on the rig and crew — a sensible skipper reefs earlier rather than later, since it's far easier and safer to reef in moderate conditions than to wait until it's genuinely blowing hard

C. Reefing only applies to the mainsail, never to a headsail

D. Reefing is a manoeuvre used exclusively when returning to harbour

A. Port and starboard change depending on which way the boat is facing

B. Port is the left-hand side and starboard is the right-hand side of the boat, when facing forward (toward the bow) — these terms are fixed to the boat itself, not to the direction you happen to be looking

C. Port refers to the front of the boat and starboard refers to the back

D. These terms are only used on larger commercial vessels, never on small craft

A. Always move as quickly as possible regardless of conditions

B. Keep one hand for yourself and one for the boat — maintain a secure handhold wherever practical, and move deliberately rather than rushing, especially in any kind of sea state

C. It doesn't matter how you move around, as long as you get where you need to be

D. Only the skipper needs to think about safe movement around the boat