This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anesthesia, Subject name: Pharmacology
A 70 kg young athlete was planned for surgery. During anesthesia,vecuronium was not available so repeated doses of succinylcholine was given intermittently up to 640mg. During recovery ,patient was not able to spontaneously respire and more limbs. What is the cause 
Select and explain. 
A. Pseudocholinestrease deficiency, B. Phase 2 blockade, C. Muscle weakness due to repeated fasiculations, D. Undiagnosed muscular dystrophy
B: Phase 2 blockade
Answer: B: Phase 2 blockade 
Explanation: Refer Wiley 7/584 Succinylcholine produces a characteristic depolarising block that is associated with absence of fade in response to train-of -four and titanic stimulation, the absence of post tetanic facilitation and increased block in the presence of anticholinesterase drugs. The type of block may change into a non depolarising type following prolonged admistration of drug