The dialysis fluid contains all the constituents of the plasma except :

The correct option is A Urea
Dialysate, also called dialysis fluid, dialysis solution or bath, is a solution of pure water, electrolytes and salts, such as bicarbonate and sodium. It contains glucose and ions in a similar concentration to that of blood but no urea. Urea is the main nitrogenous waste of the body and in case of kidney failure, this gets accumulated in the blood. The purpose of having no urea in the dialysate is to pull toxins (urea) from the blood into the dialysate.