Here's a problem to solve: Which factor best explains how many diseases, such as cancer, are formed within the body?

Among the 4 following options, which is the correct answer?

- A: A traumatic injury to the body has occurred.
 
- B: A disruption in the cell cycle has taken place.
 
- C: A response by the immune system was triggered by an allergic reaction.
 
- D: A mutation occurred during the process of crossing over.
 