**Core Concept**
The placement of a double lumen tube (DLT) is a critical step in the management of patients requiring mechanical ventilation, particularly those undergoing thoracic or abdominal surgery. A DLT is a specialized endotracheal tube that has two separate lumens, one for ventilation and the other for suction or medication administration. The correct placement of a DLT is essential to ensure adequate ventilation and prevent complications such as bronchopleural fistula or pneumothorax.

**Why the Correct Answer is Right**
The correct placement of a DLT is best confirmed by a chest X-ray (CXR), which allows for visualization of the tube's position in relation to the carina and the mainstem bronchi. This is particularly important in patients with abnormal lung anatomy or those who have undergone previous thoracic surgery. A CXR can also help identify any potential complications such as malposition or kinking of the tube.

**Why Each Wrong Option is Incorrect**
**Option A:** **Adequate ventilation and respiratory rate**. While these are important parameters to monitor, they do not confirm the correct placement of a DLT. A patient may be adequately ventilated with a malpositioned tube.

**Option B:** **Bronchoscopic visualization**. While bronchoscopy is a valuable tool for confirming DLT placement, it is not the most practical or readily available method in all clinical settings.

**Option C:** **Clinical assessment and auscultation**. While clinical assessment and auscultation can provide useful information about a patient's respiratory status, they are not reliable methods for confirming DLT placement.

**Clinical Pearl / High-Yield Fact**
A DLT should be inserted by an experienced anesthesiologist or a trained intensivist, and its placement should be confirmed by a CXR before commencing mechanical ventilation.

**Correct Answer: C. Chest X-ray (CXR)**