Given: The probability of an event must lie between \( 0 \) and \( 1 \), inclusive.
Step 1: Understanding Probability Range
- Probability of any event \( P(E) \) satisfies: \[ 0 \leq P(E) \leq 1 \]
Step 2: Checking the Given Options
- \( 0 \) is a valid probability (impossible event). - \( \frac{4}{5} = 0.8 \), which is within the valid range. - \( \frac{5}{4} = 1.25 \), which is greater than \( 1 \), so it is not a valid probability. - \( 1 \) is a valid probability (certain event).
Final Answer: \(\frac{5}{4}\)