**Core Concept**
The coeliac artery (also known as the celiac trunk) supplies blood to the liver, stomach, and pancreas. Ligation or occlusion of this artery can significantly impact these organs, leading to various clinical consequences.

**Why the Correct Answer is Right**
The coeliac artery primarily branches into the left gastric artery, common hepatic artery, and splenic artery. Ligation of the coeliac artery will mainly affect the structures supplied by these branches, including the stomach, liver, and spleen. The liver will suffer from reduced blood flow, leading to ischemia and potentially liver dysfunction. The stomach and spleen will also experience reduced perfusion, affecting their functions.

**Why Each Wrong Option is Incorrect**
**Option A:** The superior mesenteric artery (SMA) is a separate branch of the abdominal aorta that supplies blood to the midgut, including the small intestine and parts of the large intestine. Ligation of the coeliac artery does not directly affect the SMA. Therefore, structures supplied by the SMA, such as the small intestine, are not primarily affected by coeliac artery ligation.
**Option B:** The inferior mesenteric artery (IMA) supplies blood to the hindgut, including the distal colon and rectum. While the IMA is also a branch of the abdominal aorta, its territory is distinct from the coeliac artery's territory. Ligation of the coeliac artery will not directly affect structures supplied by the IMA.
**Option C:** The right gastric artery is a branch of the proper hepatic artery, which in turn is a branch of the common hepatic artery. The common hepatic artery is a direct branch of the coeliac artery. Therefore, ligation of the coeliac artery will indirectly affect the right gastric artery and the structures it supplies.

**Clinical Pearl / High-Yield Fact**
In clinical practice, ligation of the coeliac artery may be performed to control bleeding from the liver or spleen in cases of trauma. However, this procedure can lead to significant morbidity and mortality due to the potential for liver dysfunction and other complications.

**Correct Answer: D. The inferior mesenteric artery.**