**Core Concept**
The T-lymphocytes, also known as T cells, are a type of white blood cell that plays a crucial role in cell-mediated immunity. They are essential for recognizing and eliminating infected cells or tumor cells, thereby protecting the body against various pathogens and diseases.

**Why the Correct Answer is Right**
T cells recognize and interact with antigens presented by antigen-presenting cells (APCs) through their T-cell receptor (TCR). Once activated, T cells can differentiate into various subtypes, including cytotoxic T cells (CD8+ T cells), helper T cells (CD4+ T cells), and regulatory T cells. Helper T cells assist in activating B cells and other immune cells, while cytotoxic T cells directly kill infected cells or tumor cells. Regulatory T cells modulate the immune response to prevent excessive inflammation and autoimmunity.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not accurately describe the function of T-lymphocytes. While T cells do play a role in immune surveillance, their primary function is not to phagocytose foreign particles.

**Option B:** This option is incorrect as it is more characteristic of B-lymphocytes, which are responsible for producing antibodies to neutralize pathogens.

**Option C:** This option is incorrect as it is a characteristic of macrophages, which are phagocytic cells that engulf and digest foreign particles and cellular debris.

**Clinical Pearl / High-Yield Fact**
T cells are essential for long-term immune memory, allowing the body to mount a rapid and effective response to previously encountered pathogens.

**Correct Answer: D. All of the above**