## **Core Concept**
The patient's symptoms of acute hirsutism and hoarseness of voice suggest an androgen excess disorder. Hirsutism refers to excessive growth of terminal hair in women in a male-like pattern, while hoarseness of voice can be a sign of virilization. These symptoms can be caused by various conditions, including androgen-secreting tumors.

## **Why the Correct Answer is Right**
The best investigation for diagnosing the cause of acute hirsutism and hoarseness of voice in a young lady like Sushila would be to identify the source of excess androgen production. **Option C** likely represents imaging studies such as ultrasound or CT scan of the adrenal glands and ovaries. These imaging techniques are crucial for detecting androgen-secreting tumors, including adrenal tumors (e.g., adrenal carcinoma) or ovarian tumors (e.g., Sertoli-Leydig cell tumor). Identifying such a tumor would explain the acute onset of symptoms due to rapid increase in androgen levels.

## **Why Each Wrong Option is Incorrect**
- **Option A**: This could potentially represent a hormonal assay, such as testosterone levels. While measuring hormone levels is essential in the diagnostic workup, it does not directly identify the source of excess androgen production.
- **Option B**: This might represent another type of investigation, but without specifics, it's hard to directly refute. However, if it doesn't directly assess for tumors or anatomical abnormalities leading to androgen excess, it would be less appropriate as an initial best investigation.
- **Option D**: This could represent other biochemical tests or evaluations that, while useful, do not directly visualize or identify the source of androgen excess.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that while several conditions can cause hirsutism, the acute onset of severe symptoms like virilization (including hoarseness of voice) in a young woman is highly suggestive of an androgen-secreting tumor. Rapid investigation to identify and treat such a tumor is critical.

## **Correct Answer: C.**