**Core Concept**
The question is testing the ability to identify the type of malaria based on the characteristics of the schizonts and pigment seen in the blood smear. This requires knowledge of the different species of Plasmodium that cause malaria, their morphological features, and the clinical presentation.

**Why the Correct Answer is Right**
The presence of all stages of schizonts, 14-20 merozoites, and yellowish-brown pigment in the blood smear is characteristic of Plasmodium vivax infection. This is because P. vivax schizonts typically contain 14-20 merozoites and are associated with a yellowish-brown pigment called hemozoin. The presence of all stages of schizonts indicates active infection, and the number of merozoites is a key feature in differentiating between species.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is likely Plasmodium falciparum, which typically has a smaller number of merozoites (6-8) and is associated with a dark brown pigment.
* **Option B:** This option is likely Plasmodium ovale, which has a smaller number of merozoites (4-8) and is associated with a yellowish pigment.
* **Option C:** This option is likely Plasmodium malariae, which has a larger number of merozoites (12-20) but is typically associated with a brownish pigment.

**Clinical Pearl / High-Yield Fact**
Remember that P. vivax and P. ovale infections can relapse after treatment due to the presence of hypnozoites in the liver, while P. falciparum and P. malariae infections do not have this characteristic.

**Correct Answer:** D.