Kidney stones are produced due to deposition of uric acid and
a)	Silicates	b)	Minerals	c)	Calcium carbonate	d)	Calcium oxalate

(d)

During urine formation, salts and other wasters are dissolved in the filtrate and pass with it out of the kidney as urine. But sometimes, certain salts (such as calcium oxalate) do not dissolved and form crystals called calcium stones. These can partially block the flow of the urine from the kidney.