An endoscopy can be used for:

A) diagnostic purposes.
B) therapeutic purposes.
C) both diagnostic and therapeutic purposes.
D) neither diagnostic nor therapeutic purposes.

Endoscopy can be both diagnostic (to visualize internal organs for abnormalities or disease) and therapeutic (to remove polyps, stop bleeding, or place stents). Therefore, option C is correct. Option A is incorrect because endoscopy is frequently used for diagnostic purposes. Option B is incorrect because endoscopy is also an interventional or therapeutic procedure. Option D is obviously incorrect; it is used to solve medical issues.