The period during which an excitable membrane can respond again, but only if the stimulus is greater than the threshold stimulus, is the period.

The correct answer is - relative refractory period.

Explanation:

The relative refractory period is a period that stimulates a secondary response if the stimuli are greater than the normal. It occurs when partial repolarization after a nerve fiber fired.

The relative refractory period is one of the two types of the refractory period which is the relative and absolute refractory period. In the absolute refractory period, it is not possible to activate another action potential in membrane.

Thus, the correct answer is -  relative refractory period.

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