This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General physiology, Subject name: Physiology
During regulatory volume decrease, many cells will increase 
Select and explain. 
A. Their volume, B. Influx of Na+, C. Efflux of K+, D. Synthesis of sorbitol
C: Efflux of K+
Answer: C: Efflux of K+ 
Explanation: K+ is the major intracellular ion; efflux of K+ will produce an osmotic flow of water out of the cell. Water exit will lead to a decrease in cell volume.An influx of Na+ and synthesis of sorbitol do not occur during this process because both processes would increase intracellular osmolytes and drive water into the cell, increasing cell volume.Ref: Guyton; 13th edition