A "fail-safe" requirement means:

Question

Options

• AThe system is safe from failure.
• BThe system will fall in a safe state.
• CThe system has safety devices.
• DThe safety systems cannot fail.

• A
  6% (2)
• B
  79% (27)
• C
  12% (4)
• D
  3% (1)

Explanation

Fail-safe means that when a system fails, it defaults to a safe condition rather than a dangerous one - this is exactly what B captures. A railway signal that defaults to "red" (stop) when the electronics fail is a classic example: the failure itself produces a safe outcome.

Why the distractors are wrong:

• A is wrong because "fail-safe" makes no promise that failure won't occur - it only controls what happens when it does.
• C is wrong because having safety devices is a broader design strategy; it doesn't specifically mean the failure mode is safe.
• D is wrong because no system can guarantee safety systems never fail - that would be an impossible standard. Fail-safe is about failure behavior, not failure prevention.

Memory tip: Break the phrase apart - "fail" then "safe." The system fails, and the result is safe. If the phrase meant preventing failure (A or D), it would be called "fail-proof" or "fail-prevent."

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