**Core Concept**
Plasmodium infections cause malaria, a disease characterized by the destruction of red blood cells (RBCs) by the parasite. The parasite's lifecycle involves multiple stages, including the erythrocytic stage, where it invades and multiplies within RBCs. Different Plasmodium species have varying predilections for specific stages of RBCs.

**Why the Correct Answer is Right**
Plasmodium vivax infection has a predilection for attacking old RBCs. This is because P. vivax parasites prefer to infect RBCs that are 2-3 days old, which have a higher concentration of hemoglobin and are more favorable for parasite growth. The parasite's invasion of old RBCs leads to their premature destruction, resulting in the characteristic symptoms of P. vivax malaria, such as relapsing fever.

**Why Each Wrong Option is Incorrect**
* **Option A:** Plasmodium falciparum, the most virulent species, primarily infects young RBCs. This species is responsible for the deadliest form of malaria, with a high morbidity and mortality rate.
* **Option B:** Plasmodium ovale also infects young RBCs, similar to P. falciparum. However, it is less virulent and has a lower parasite load compared to P. falciparum.
* **Option D:** Plasmodium malariae infects middle-aged RBCs, not old RBCs. This species is characterized by its ability to cause long-term infection, leading to chronic malaria symptoms.

**Clinical Pearl / High-Yield Fact**
P. vivax parasites can remain dormant in the liver as hypnozoites, leading to relapses of the disease even after apparent recovery. This is a crucial consideration for treatment and management of P. vivax malaria.

**Correct Answer: C. Plasmodium vivax**