**Core Concept**
Lithotripsy is a medical procedure that uses shock waves to break down stones in the urinary tract into smaller pieces that can then be easily passed out of the body. The effectiveness of lithotripsy depends on the composition and characteristics of the stone.

**Why the Correct Answer is Right**
Some types of stones are resistant to lithotripsy due to their composition. Specifically, uric acid stones and cystine stones are more likely to be resistant to lithotripsy because they are softer and more prone to disintegration with the application of heat or other energy sources. In contrast, calcium oxalate stones are more likely to be resistant to lithotripsy because they are harder and less prone to disintegration.

**Why Each Wrong Option is Incorrect**
* **Option A:** Struvite stones are not typically resistant to lithotripsy. They are often caused by urinary tract infections and are composed of magnesium ammonium phosphate.
* **Option B:** Xanthine stones are rare and not typically resistant to lithotripsy. They are often associated with xanthinuria, a rare genetic disorder.
* **Option C:** Calcium phosphate stones are not typically resistant to lithotripsy. They are often associated with hyperparathyroidism and are composed of calcium phosphate.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the composition of the stone and the location of the stone in the urinary tract can affect the success of lithotripsy. Stones located in the lower pole of the kidney are often more challenging to treat with lithotripsy.

**Correct Answer: C. Calcium oxalate stones.**