- 0
- 1
- 0.50
- 0.33
- 0.88
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Answer: B official key
Approach: Time comparison in a race — certain event has probability 1.
Solution:
A runs the full 400 m: time = 400 ÷ 10 = 40 s.
B starts 50 m ahead, so runs 350 m: time = 350 ÷ 8 = 43.75 s.
A always finishes 3.75 s earlier — no chance involved.
An event that is certain has probability 1.
Why the other options are wrong:
A: 0 would mean A can never win.
C, D, E: fractional values imply uncertainty, but the speeds fix the result.
Cetking shortcut: Head start 50 m at 8 m/s is worth 6.25 s, but A already gains 10 s over 400 m (50 vs 40 s) — A wins for sure.
Answer: B








