**Core Concept**
The question is testing the ability to identify the most potent stimulator of naive T-cells. Naive T-cells are a subset of T-cells that have not yet encountered their specific antigen and require activation to become effector T-cells. The stimulator in question likely refers to a substance that can activate naive T-cells by interacting with their T-cell receptor (TCR) or other surface molecules.

**Why the Correct Answer is Right**
The most potent stimulator of naive T-cells is **Antigen-presenting cells (APCs) presenting peptide-MHC complexes**. APCs, such as dendritic cells, capture and process antigens, then present peptide fragments on their surface bound to MHC class I or II molecules. This presentation of peptide-MHC complexes to the TCR on naive T-cells is the primary mechanism of T-cell activation. The interaction between the TCR and peptide-MHC complex triggers a cascade of intracellular signaling events, leading to the activation of naive T-cells.

**Why Each Wrong Option is Incorrect**
* **Option A:** While cytokines, such as IL-2, can support T-cell activation and proliferation, they are not the most potent stimulators of naive T-cells.
* **Option B:** Antigen itself, in the absence of APC presentation, is not sufficient to activate naive T-cells.
* **Option C:** Antibodies can activate T-cells through Fc receptors, but this is not the primary mechanism of naive T-cell activation.

**Clinical Pearl / High-Yield Fact**
Naive T-cells require a strong signal from APCs to become activated, and this process is often referred to as "signal 1". The second signal, or "signal 2", is provided by costimulatory molecules on APCs, such as B7-1 and B7-2, which interact with CD28 on T-cells.

**Correct Answer: D. Antigen-presenting cells (APCs) presenting peptide-MHC complexes**