This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
Cell membrane of a cell is freely permeable to three ions X, Y and Z. At resting membrane potential, the respective equilibrium potentials of Xand Y are -30mV and -40 mV.What will happen to the membrane potential if a drug is infused which can block the permeability of Z? 
Select and explain. 
A. Depolarisation, B. Hyperpolarization, C. No change, D. Hyperpolarization following repolarization
A: Depolarisation
Answer: A: Depolarisation 
Explanation: Ans. A. DepolarisationRef: Guyton & Hall 13' ed., ch-5, pg. 61-63.In this question if Z has a reversal potential or original RMP was more negative (e.g., -70 or -90 mV) then closure of C ion channels would shift the RMP closer to reversal potential of A, B thus depolarising the cell