Passage: "At roll call the sergeant assigned Trooper A to the north sector, Trooper B to the south sector, and Trooper C to relieve whoever finished first." If Trooper A finishes the north sector first, what is Trooper C's assignment?

1. To relieve Trooper A in the north sector
2. To go off duty
3. To relieve Trooper B
4. To return to roll call