<prompt> Concentration of urea on one side side A of permeable membrane is 20 and on other side side B is 40. If concentration on side A is increased to 40, what will happen to rate of diffusion?It will become doubleIt will become four timesIt will be zeroIt will be reduced four times  <response>: Ans. is c i.e., It will be zero Ref: Principles of medical physiology p. 71This question, the concentration gradient is zero as both sides A B have same concentration 40 of urea.Thus there is no diffusion Rate of diffusion is zero. 