Which of the following requirements statements is written in such a way that it can...

A validatable requirement must be clear, measurable, testable, and objective. The statement that the system shall be available at least 99.98% of the time provides a specific measurable threshold. Testers and quality engineers can verify it using availability measurements, operational logs, downtime records, or reliability monitoring over a defined period. Option A is weak because “some signals” is vague and does not define which signals must cause which response. Option B is not independently testable because “according to user requirements” refers to another undefined set. Option C says response time is operator defined, but it does not specify an acceptable value or condition. Since option D includes a measurable acceptance criterion, it is the best validated requirement.

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