**Core Concept**
The phrenic nerves are essential for the motor control and sensory innervation of the diaphragm, a critical muscle for respiration. The right phrenic nerve, originating from the cervical spine, must traverse the diaphragm to reach its target muscle.

**Why the Correct Answer is Right**
The right phrenic nerve passes through the **vena caval opening**, also known as the vena cava foramen. This opening is located in the posterior part of the diaphragm, allowing the right phrenic nerve and the inferior vena cava to pass through. The vena cava foramen is a significant anatomical landmark, and its location is crucial for surgeons to avoid during thoracic and abdominal surgeries.

**Why Each Wrong Option is Incorrect**
**Option A:** The **oesophageal opening** is incorrect because it is primarily used by the oesophagus and the branches of the vagus nerve, not the phrenic nerve.
**Option B:** The **aortic opening** is incorrect because it is used by the aorta and its branches, not the phrenic nerve.
**Option C:** The **oesophageal hiatus** is incorrect because it is a separate opening for the oesophagus and vagus nerve branches, not the phrenic nerve.

**Clinical Pearl / High-Yield Fact**
The phrenic nerves are responsible for the motor innervation of the diaphragm, but they also provide sensory innervation to the central part of the diaphragm and the mediastinal pleura. This sensory innervation is essential for the transmission of pain and other sensations from the diaphragm and surrounding structures.

**Correct Answer: C. aortic opening**