**Core Concept**
Immune complex mediated hypersensitivity, also known as type III hypersensitivity, occurs when antigen-antibody complexes accumulate in the body and deposit in tissues, leading to inflammation and tissue damage. This process involves the activation of complement system, which results in the formation of membrane attack complex (MAC) and release of anaphylatoxins.

**Why the Correct Answer is Right**
The correct answer involves the deposition of antigen-antibody complexes in tissues, which activates the complement system. This leads to the formation of MAC, causing cell lysis and tissue damage. The anaphylatoxins released during this process cause vasodilation, increased vascular permeability, and smooth muscle contraction, resulting in the characteristic symptoms of immune complex mediated hypersensitivity, such as fever, arthralgias, and skin rash.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because immune complex mediated hypersensitivity does not involve the direct activation of T cells or B cells. Instead, it involves the deposition of antigen-antibody complexes in tissues.
**Option B:** This option is incorrect because cytotoxic T cell mediated hypersensitivity (type II) involves the direct killing of cells by T cells, rather than the deposition of antigen-antibody complexes.
**Option C:** This option is incorrect because delayed hypersensitivity (type IV) involves the activation of T cells, rather than the deposition of antigen-antibody complexes.

**Clinical Pearl / High-Yield Fact**
Immune complex mediated hypersensitivity can be seen in conditions such as systemic lupus erythematosus (SLE), rheumatoid arthritis, and post-streptococcal glomerulonephritis, where there is an accumulation of antigen-antibody complexes in tissues.

**Correct Answer:** A. Type III hypersensitivity.