A SIS operates in low-demand mode with a proof test interval of 1 year. If one proof test reveals a failure that has been present since the last test, what does this indicate about the PFD calculation?
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A
The Mission Time must be reduced
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B
The average PFD (PFDavg) accounts for this by averaging the probability of being in a failed state over the full test interval
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C
The SIL target must be increased by one level
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D
The diagnostic test interval must be shortened to match the proof test interval