If the probability of an event is p, then which of the following holds true?

1. −1 ≤ p ≤ 1

2. 0 ≤ p ≤ ∞

3. 0 ≤ p ≤ 1

4. −∞ < p < ∞

Probability is a measure of the likelihood of an event occurring, and it must always fall within a specific range:

0 ≤ p ≤ 1

Hence, option 3 is the correct option.