This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Neuromuscular Blocker, Subject name: Anaesthesia
What is defined as recovery index of the neuromuscular blocker (NMB):- 
Select and explain. 
A. It is time interval between 25% and 75% twitch height of the NMB, B. It is time interval between 25% and 50% twitch height of the NMB, C. It is time interval between 50% and 75% twitch height of the NMB, D. It is time interval to reach 100% of twitch height of the NMB
A: It is time interval between 25% and 75% twitch height of the NMB
Answer: A: It is time interval between 25% and 75% twitch height of the NMB 
Explanation: Duration of action is the time from injection of the neuromuscular blocking agent to return of 25% twitch height. Recovery index is the time interval between 25% and 75% twitch height.