**Core Concept**
The patient's presentation of painless gross hematuria in a 60-year-old smoker suggests a high suspicion for urothelial carcinoma, particularly transitional cell carcinoma (TCC) of the bladder. This type of cancer is more common in older adults and is often associated with smoking.

**Why the Correct Answer is Right**
The most logical investigation for this patient is a cystoscopy with biopsy, as it allows direct visualization of the bladder mucosa and enables the collection of tissue samples for histopathological examination. Cystoscopy has a high sensitivity for detecting bladder tumors, especially those that are visible to the naked eye. The presence of painless gross hematuria is a red flag symptom for bladder cancer, and a thorough evaluation is warranted.

**Why Each Wrong Option is Incorrect**
**Option A:** Urinalysis would be an initial step in evaluating hematuria but would not be the most logical next step in a patient with painless gross hematuria and a strong smoking history.

**Option B:** Abdominal ultrasound may be useful in evaluating the kidneys and upper urinary tract but is not the most appropriate initial investigation for a patient with a strong suspicion of bladder cancer.

**Option C:** CT urography is a useful imaging modality for evaluating the upper urinary tract but may not be the best initial choice for a patient with painless gross hematuria and a strong suspicion of bladder cancer.

**Clinical Pearl / High-Yield Fact**
In patients with painless gross hematuria and a strong smoking history, bladder cancer should be a top differential diagnosis, and a prompt evaluation with cystoscopy and biopsy is essential to establish an accurate diagnosis and initiate appropriate treatment.

**Correct Answer:** C.