I think its the first one
Difference threshold is a minimum alteration in sensory intensity that is noticeable to an observer and can be coded into neural messages. Different threshold is the lowest level of encouragement that is essential to sense that a modification has happened the difference in the intensity between two stimuli that is necessary to yield a just notable difference also known as JND. The just notable difference depends not only on the intensity of the new stimulus but also on the level of stimulation already present which is the more intense the existing stimulus the larger the change must be to be noticeable.
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When a stem cell divides, each new cell has the potential to either remain a stem cell or become another type of cell with a more specialized function, such as a muscle cell, a red blood cell or a brain cell. There are three characteristics of all stem cells.
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