**Core Concept**
The most common type of bladder cancer is a neoplasm that arises from the urothelial lining of the bladder, which is the epithelial layer that lines the bladder's inner surface. Urothelial carcinomas are also known as transitional cell carcinomas and are the most prevalent type of bladder cancer.

**Why the Correct Answer is Right**
Urothelial carcinomas arise from the urothelial cells that line the bladder, and their development is associated with exposure to carcinogens, such as tobacco smoke, and other environmental factors. The most common histological subtype of urothelial carcinoma is papillary urothelial carcinoma, which typically presents as a non-muscle-invasive tumor. This type of cancer tends to grow on the bladder's surface and is often detected early through symptoms or screening.

**Why Each Wrong Option is Incorrect**
* **Option A:** Squamous cell carcinoma is a type of bladder cancer that arises from the squamous epithelium, which is not the most common type of bladder cancer. It is more commonly associated with chronic irritation or inflammation.
* **Option B:** Adenocarcinoma of the bladder is a rare type of bladder cancer that arises from glandular cells. It is not the most common type of bladder cancer.
* **Option C:** Small cell carcinoma is a rare and aggressive type of bladder cancer that is often associated with smoking. It is not the most common type of bladder cancer.

**Clinical Pearl / High-Yield Fact**
The most common symptom of bladder cancer is painless hematuria, or blood in the urine. This symptom is often detected during routine urinalysis or self-examination.

**Correct Answer:** C.