Measurements for excitation are: Depolaris tion, hyperpolarisation; Repolaris ation, polarisation; Threshold, useful time, lability; Action potential , refractoriness.

The correct answer is: Threshold, useful time, lability.<br /><br />Explanation: In the context of neuronal excitability, the terms 'threshold,' 'useful time,' and 'lability' are relevant. Threshold refers to the critical level of depolarization that must be reached for an action potential to occur. Useful time is the duration during which a neuron can effectively respond to a stimulus. Lability indicates the ease with which a neuron can be excited. The other options, such as depolarization, hyperpolarization, repolarization, and polarisation, are related to the phases of the action potential, while action potential and refractoriness describe the overall process and its timing, respectively.