**Core Concept**
Multiple infection of RBC is a phenomenon where a single red blood cell is parasitized by multiple merozoites of the malaria parasite, Plasmodium falciparum. This leads to a condition known as rosetting, where the infected RBCs clump together, causing microvascular obstruction and severe complications.

**Why the Correct Answer is Right**
The correct answer is due to the unique biology of Plasmodium falciparum, which can invade and infect RBCs at different stages of its life cycle. When multiple merozoites infect a single RBC, they can cause the cell to become rigid and adhere to other infected RBCs, forming rosettes. This process is mediated by the interaction between the parasite's surface proteins and the RBC membrane, leading to the characteristic "dark, ring-shaped" appearance under microscopy. The rosetting phenomenon is a key factor in the pathogenesis of severe malaria, particularly in cerebral malaria.

**Why Each Wrong Option is Incorrect**
**Option A:** Other malaria parasites like Plasmodium vivax and Plasmodium ovale do not typically cause multiple infection of RBCs. They are less likely to form rosettes and cause severe complications.
**Option B:** Babesia, a different type of parasite that infects RBCs, does not cause multiple infection of RBCs. Babesia parasites typically invade RBCs in a single cell and cause hemolysis, but do not form rosettes.
**Option C:** Trypanosomes, which cause African trypanosomiasis, do not infect RBCs. They are extracellular parasites that infect other cells and tissues, and do not cause multiple infection of RBCs.

**Clinical Pearl / High-Yield Fact**
The "ring-shaped" appearance of Plasmodium falciparum-infected RBCs under microscopy is a key diagnostic feature, but it can be challenging to detect, especially in early stages of infection. Clinicians should consider the clinical context and perform additional tests, such as PCR or rapid diagnostic tests, to confirm the diagnosis.

**Correct Answer:** D.