**Core Concept**
Apoptosis is a form of programmed cell death, a regulated process by which cells undergo a series of cellular changes leading to their death without inducing inflammation. This process is essential for normal development, tissue homeostasis, and removal of damaged or unwanted cells.

**Why the Correct Answer is Right**
All the options listed are indeed examples of apoptosis. Graft versus host disease is a form of immune-mediated apoptosis, where the immune cells from the donor recognize the host cells as foreign and induce apoptosis. Menstrual cycle involves apoptosis of the endometrial cells, which is a physiological process necessary for reproductive health. Pathological atrophy following duct obstruction, such as in the case of a blocked salivary gland, also involves apoptosis of the cells lining the duct.

**Why Each Wrong Option is Incorrect**
**Option A:** Graft versus host disease is indeed an example of apoptosis, where immune cells induce programmed cell death.
**Option B:** Menstrual cycle is also an example of apoptosis, where endometrial cells undergo programmed cell death.
**Option C:** Pathological atrophy following duct obstruction is an example of apoptosis, where cells lining the duct undergo programmed cell death.

**Clinical Pearl / High-Yield Fact**
It is essential to recognize that apoptosis is a vital process for maintaining tissue homeostasis and preventing cancer. Dysregulation of apoptosis can lead to various diseases, including cancer and autoimmune disorders.

**✓ Correct Answer: D. None. None of the options are exceptions to apoptosis.**