The difference threshold is:

A. the difference between an amount of stimulus too small to detect and an amount of stimulus too great to tolerate
B. the minimal difference between two stimuli that people can reliably detect.
C. the difference in how any two people tolerate a stimulus.
D. the difference in how any two people are able to detect a minimal amount of a stimulus.
E. the phenomenon that everyone has a different threshold for a given stimulus.

the minimal difference between two stimuli that people can reliably detect

Explanation:

A difference threshold is the minimum amount that something needs to change in order for a person to notice a difference 50% of the time. It is sometimes called  the just noticeable difference (jnd), and it depends on the strength of the stimulus.

the minimal difference between two stimuli that people can reliably detect, also called just-noticeable difference. the amount of change in a stimulus need to detect a difference, expressed as a constant ratio or fraction of the original stimulus

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