Inspector Holmes and His Trusty Assistant, Watson, Are Snooping Around

Inspector Holmes and his trusty assistant, Watson, are snooping around a dark, deserted house in London. Watson suddenly screams, "Holmes! I thought I just saw a flicker of light!" Holmes turns to him and says, "No, my dear boy. You must have been interpreting a random firing of sensory neurons as a stimulus." Holmes was describing

A) absolute threshold.
B) just-noticeable difference.
C) internal noise.
D) Weber's law.