**Core Concept**
The presentation of gross haematuria in an elderly male requires a thorough investigation to rule out underlying malignancies, infections, or other causes. **Urinary tract infections**, **kidney stones**, and **bladder cancer** are common considerations.

**Why the Correct Answer is Right**
Since the correct answer is not provided, let's consider the general approach to investigating gross haematuria. A typical workup includes **urinalysis**, **imaging studies** like ultrasound or CT scans, and **cystoscopy** to directly visualize the bladder and urethra.

**Why Each Wrong Option is Incorrect**
**Option A:** Without the specific option, we can't comment directly, but typically, a **urine culture** would be appropriate to check for infections.
**Option B:** Similarly, without specifics, if this option involved **imaging**, it would be relevant for identifying structural issues.
**Option C:** If this involved **cystoscopy**, it's a crucial step for visualizing the bladder and urethra.
**Option D:** Assuming this might involve an unnecessary or inappropriate test, it would be incorrect based on not being a standard initial step in the workup.

**Clinical Pearl / High-Yield Fact**
In patients with gross haematuria, it's crucial to consider the risk factors for **bladder cancer**, such as smoking and age. A thorough investigation, including **cystoscopy** and **upper tract imaging**, is essential for diagnosing the cause of haematuria.

**Correct Answer:** Correct Answer: D. Total body CT scan.