Increase in threshold level on applying subthreshold, slowly rising stimulus is known as: (A) Adaptation, (B) Accomodation, (C) Refractoriness, (D) Electrotonus
Answer is B. Accommodation- Slow rising subthreshold stimulus failing to produce action potential even when the normal threshold levels are reached. This occurs because of inactivation of voltage-gated Na+ channels. 
Adaptation- Persistent application of suprathreshold stimulus fails to generate repetitive firing.
Refractoriness- A stimulus to the nerve does not elicit a response.
Electrotonus- When a current is passed through electrodes kept on the surface of a nerve, current passes through it resulting in a change in membrane potential and development of electrotonic potential.