**Core Concept**
Glomerulonephritis is a group of kidney diseases characterized by inflammation of the glomeruli, the filtering units of the kidneys. This condition is often caused by an abnormal immune response, leading to damage to the glomeruli and impaired kidney function.

**Why the Correct Answer is Right**
Immune complex deposition is the correct answer because it is a key mechanism underlying many types of glomerulonephritis. In this process, circulating antibodies bind to antigens, forming immune complexes that deposit in the glomeruli. This triggers an inflammatory response, leading to glomerular damage and dysfunction. The immune complexes can also activate complement and stimulate the release of various cytokines, further exacerbating the inflammatory response. The deposition of immune complexes in the glomeruli is a hallmark of conditions such as lupus nephritis and post-streptococcal glomerulonephritis.

**Why Each Wrong Option is Incorrect**
**Option A:** Type I hypersensitivity reactions, also known as immediate hypersensitivity reactions, involve the release of histamine and other mediators from mast cells and basophils. This type of reaction is not typically associated with glomerulonephritis.

**Option B:** Type IV hypersensitivity reactions, also known as delayed hypersensitivity reactions, involve the activation of T cells and the release of cytokines. While T cell activation can contribute to the inflammatory response in glomerulonephritis, this is not the primary mechanism underlying the condition.

**Option D:** Type V hypersensitivity reactions are not a recognized classification of hypersensitivity reactions. This option is likely a distractor and is not a valid answer.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that glomerulonephritis can be caused by a variety of factors, including infections, autoimmune disorders, and systemic diseases. Immune complex deposition is a key mechanism underlying many types of glomerulonephritis, and understanding this process is critical for diagnosing and managing these conditions.

**✓ Correct Answer: C. Immune complex deposition**