**Core Concept**
The aortic hiatus is a diaphragmatic opening that allows vital structures to pass between the thoracic and abdominal cavities. This diaphragmatic opening is crucial for the passage of several important structures, and identifying these structures is essential for understanding thoracic-abdominal relationships.

**Why the Correct Answer is Right**
The correct structures passing through the aortic hiatus are the aorta and the thoracic duct. The aorta, being the main artery supplying oxygenated blood to the body, requires a passage through the diaphragm to descend into the abdominal cavity. The thoracic duct, on the other hand, is the primary lymphatic vessel responsible for draining lymph from the lower limbs and abdominal organs, eventually returning to the bloodstream. This passage is essential for the proper functioning of both the circulatory and lymphatic systems.

**Why Each Wrong Option is Incorrect**
**Option A:** The esophagus passes through the esophageal hiatus, not the aortic hiatus. The esophageal hiatus is located more inferiorly and allows the esophagus to connect the thoracic cavity to the abdominal cavity.
**Option B:** The phrenic nerves do not pass through the aortic hiatus. Instead, they pass through the diaphragmatic foramina to innervate the diaphragm.
**Option C:** The vagus nerve does not pass through the aortic hiatus. The vagus nerve has various branches that pass through different diaphragmatic openings, but it is not associated with the aortic hiatus.
**Option D:** The sympathetic trunk does not pass through the aortic hiatus. The sympathetic trunk is a chain of sympathetic ganglia that runs along the vertebral column, but it does not require a passage through the aortic hiatus.

**Clinical Pearl / High-Yield Fact**
The aortic hiatus is located at the level of the T12 vertebra, and it is a significant landmark for identifying the diaphragm's position on radiographic images. The passage of vital structures through this hiatus is essential for understanding thoracic-abdominal relationships and the clinical implications of diaphragmatic hernias or other pathologies.

**Correct Answer:** A. Aorta and thoracic duct