## **Core Concept**
The question tests knowledge of antimalarial drugs, specifically those effective against *Plasmodium falciparum* and *Plasmodium vivax*, including strains resistant to chloroquine. The focus is on a drug that can provide a clinical cure with a single oral dose.

## **Why the Correct Answer is Right**
The correct answer, **Artesunate**, is a derivative of artemisinin, which is known for its rapid action against malaria parasites, including *P. falciparum* and *P. vivax*. Artesunate is effective against strains of *P. falciparum* that are resistant to chloroquine. When used as a single oral dose or in combination therapy, it can provide a rapid reduction in parasitemia, effectively curing uncomplicated malaria caused by both chloroquine-sensitive and resistant strains of *P. falciparum* as well as *P. vivax*.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because, although some antimalarials are effective against *P. falciparum*, they may not be as effective against *P. vivax* or may not offer a single-dose cure.
- **Option B:** This option is incorrect as it likely represents a drug that is not as effective against both *P. falciparum* and *P. vivax*, particularly in cases of chloroquine resistance.
- **Option D:** This option is incorrect because it probably represents a drug that requires multiple doses or is not effective as a monotherapy for a single dose cure.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that **artemisinin-based combination therapies (ACTs)**, including artesunate, are recommended by the World Health Organization (WHO) for the treatment of uncomplicated *P. falciparum* malaria. Artesunate, in particular, is noted for its efficacy and rapid action. For *P. vivax* malaria, treatment often includes chloroquine (for sensitive strains) plus primaquine to eliminate liver stages, but artesunate can be effective.

## **Correct Answer:** C. Artesunate.