Answer: a) respiratory arrest
Explanation: the neuro-muscular blocking agent causes muscles to relax, respiration is vital for oxygen intake and and proper functioning of vital organs. Respiration depends on the diaphragm muscles for the expansion and contraction of the lungs; administration of NMBA can hamper the diaphragm muscles and this could be fatal hence, respiratory arrest should be watched out for.
Four times greater.
Laws of physics state that force will always be the result of the square of the speed. For example, if you tripled the speed the impact would be 9 times.