A linear scan stops when it finds its target. Which statement is precise?

A linear scan stops when it finds its target. Which statement is precise?

1. Its time is always Θ(1).
2. Its best case is Θ(1), while its worst case is Θ(n).
3. Its average case is automatically Θ(n / 2).
4. Its worst case is Θ(n²).