**Core Concept**
The question is testing knowledge about the types of bladder stones, which are formed due to the concentration of minerals in the urine. Bladder stones can be composed of various substances, including struvite, calcium oxalate, uric acid, and cystine.

**Why the Correct Answer is Right**
The correct answer is struvite stones, which are often associated with urinary tract infections (UTIs) caused by urease-producing bacteria like Proteus. These bacteria break down urea to ammonia, increasing the pH of the urine and promoting the formation of struvite stones. Struvite stones are typically radiolucent, meaning they are not visible on plain X-rays, and are often found in women with recurrent UTIs.

**Why Each Wrong Option is Incorrect**
**Option A:** Calcium oxalate stones are more common in the kidneys than in the bladder. They are often associated with hypercalciuria, hyperoxaluria, or conditions like kidney stones.
**Option B:** Uric acid stones are more commonly found in patients with gout or those on certain medications. They tend to form in acidic urine and are often associated with conditions like kidney stones.
**Option C:** Cystine stones are rare and occur in patients with cystinuria, a genetic disorder that affects the kidneys and intestines. They are more commonly found in the kidneys than in the bladder.

**Clinical Pearl / High-Yield Fact**
Struvite stones are often associated with UTIs, especially in women. A high index of suspicion for UTIs should be maintained in patients with recurrent bladder stones.

**Correct Answer: A. Struvite stones.**