Under ICAO Doc 4444 (PANS-ATM) and Annex 6, what is communicated to air traffic control when a flight crew declares 'MAYDAY, MAYDAY, MAYDAY, FUEL'?

1. The aircraft has sufficient fuel to hold for two additional hours without deviation
2. The calculated usable fuel predicted to be available upon landing at the nearest aerodrome is less than the planned final reserve fuel, requiring immediate priority handling
3. The flight crew wishes to purchase extra fuel upon arrival at the gate
4. The aircraft has suffered an external fuel leak that has already been extinguished