A sailboat is moving at a constant velocity.

1. Four external forces are acting on the boat but no net work is done.
2. Three external forces are acting on the boat but no net work is done.
3. Two external forces are acting on the boat but no net work is done.
4. Four external forces are acting on the boat and positive net work is done.
5. Four external forces are acting on the boat but negative net work is done.