<prompt> Which of the following stones is hard to break by ESWL:Calcium Oxalate MonohydrateCalcium Oxalate DihydrateUric acidStruvite  <response>: Answer is A Calcium Oxalate Monohydrate: Calcium Oxalate Monohydrate Stones and cysteine stones are very hard to break by ESWL. Very hard stones such as cysteine or calcium oxalate monohydrate are more likely to fail ESWL. Likelihood offragmentation with ESWL depends on stone composition. Less effective for stones composed of cystine or calcium oxalate monohydrate very hard - Oxford handbook of urology 2005366 Softer stones calcium oxalate dehydrate, uric acid, apatite, and struvite are more easily fragmented with SWL than are harder stones calcium oxalate monohydrate, brushite, and cystine - 