**Core Concept**
P. falciparum is a species of Plasmodium that causes malaria, and its lifecycle involves infecting erythrocytes (red blood cells) at various stages. Understanding the specific characteristics of each Plasmodium species, including their preferred red blood cell targets, is crucial for diagnosing and treating malaria.

**Why the Correct Answer is Right**
P. falciparum is known to infect a wide range of red blood cell ages, not just young ones. This characteristic allows it to evade the spleen's filtering mechanism, which primarily targets older, damaged red blood cells. In contrast to other Plasmodium species, P. falciparum can infect both young and old red blood cells, making it more virulent and difficult to treat.

**Why Each Wrong Option is Incorrect**
**Option A:** P. vivax typically infects red blood cells that are less than 10 days old, not specifically under 14 days. This distinction is crucial for understanding the lifecycle of P. vivax.
**Option C:** While it is true that P. ovale selectively infects reticulocytes (young red blood cells), this statement does not address the specific error in the original statement about P. falciparum. However, P. ovale does indeed have a predilection for reticulocytes.
**Option D:** P. malariae is known to infect older red blood cells, which is the opposite of the original statement's claim about P. falciparum.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that P. falciparum's ability to infect a wide range of red blood cell ages contributes to its high virulence and resistance to the spleen's filtering mechanism. This characteristic makes it particularly challenging to treat and emphasizes the need for prompt and effective antimalarial therapy.

**✓ Correct Answer: B. P. falciparum infects young RBC's only**