**Core Concept**
The question pertains to the development of a vaccine against Plasmodium falciparum, the parasite responsible for the deadliest form of malaria. The correct vaccine strain is a crucial aspect of vaccine development, as it determines the efficacy and safety of the vaccine.

**Why the Correct Answer is Right**
The RTS,S vaccine, developed by GlaxoSmithKline, is the first and only malaria vaccine to be licensed for use in humans. It is a recombinant protein-based vaccine that targets the circumsporozoite protein (CSP) of Plasmodium falciparum, which is responsible for the parasite's invasion of liver cells. The vaccine has undergone rigorous clinical trials and has been shown to provide partial protection against malaria in young children.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the RTS,S vaccine is the only malaria vaccine to have been licensed for use in humans, and it targets the CSP protein of Plasmodium falciparum.
* **Option B:** This option is incorrect because the PfSPZ vaccine, also known as Mosquirix, is a different malaria vaccine that targets the CSP protein of Plasmodium falciparum, but it is not the vaccine strain mentioned in the question.
* **Option C:** This option is incorrect because it does not specify a known malaria vaccine strain, and it is not relevant to the RTS,S vaccine.

**Clinical Pearl / High-Yield Fact**
The RTS,S vaccine is the result of decades of research and development, and its licensure marks a significant milestone in the fight against malaria. However, it is essential to note that the vaccine provides only partial protection against malaria, and it should be used in conjunction with other control measures, such as insecticide-treated bed nets and indoor residual spraying.

**Correct Answer: RTS,S**