This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
Brachytherapy is: 
Select and explain. 
A. Irradiation of tissues from a distance, B. Irradiation of tissues from a distance of 3 cm, C. Irradiation of tissues by implants within the tissues, D. Irradiation of tissues by radiopharmaceuticals
C: Irradiation of tissues by implants within the tissues
Answer: C: Irradiation of tissues by implants within the tissues 
Explanation: None