An endoscope allows for entry into the body through which of the following?

An endoscope is a versatile medical instrument designed for visualizing the interior of a body cavity or organ. It can be introduced into the body through various entry points, which is why the correct answer encompasses all provided options.

The endoscope can enter the body via natural orifices such as the mouth, nose, and anus, allowing for procedures in areas like the gastrointestinal tract. It can also be inserted through small incisions made in the skin, especially in minimally invasive surgeries. Additionally, it can access externalized sinus tracts, which are abnormal passages that can form on the skin's surface. This flexibility in entry methods makes endoscopy a valuable tool in both diagnostic and therapeutic procedures across many medical fields, including gastroenterology, pulmonology, and urology.

Each entry method serves specific clinical purposes, demonstrating the overall utility of the endoscope in modern medicine. Thus, the comprehensive answer that includes all types of access points reflects the endoscope's adaptability.