**Core Concept**
The question tests the understanding of **metastasis** and **tumor spread** in the context of **peritoneal cancer**. The most common site of origin for peritoneal deposits is related to the **gastrointestinal tract**, specifically the **ovary** in females.

**Why the Correct Answer is Right**
The correct answer is related to the **ovary**, as **ovarian cancer** is known to spread intraperitoneally, leading to peritoneal deposits. This occurs due to the **transcoelomic spread** of cancer cells from the ovary to the peritoneal cavity.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect as it is not the most common site.
**Option B:** Incorrect as it is not directly related to peritoneal deposits.
**Option C:** Incorrect as it is not the primary site for peritoneal cancer.
**Option D:** Incorrect, not the most common site of origin.

**Clinical Pearl / High-Yield Fact**
Ovarian cancer is a classic example of a **transcoelomic spread**, where cancer cells disseminate throughout the peritoneal cavity, leading to peritoneal deposits.

**Correct Answer:** D. Ovary