Answer: C. to show that the students have tried hard to solve the question.
Explanation:
The term "battle zone" symbolizes the situation in which the students try as hard as they can to answer the questions. They are trying to 'fight' the questions - solving the questions means "victory."
Option A is incorrect, as there is unlikely a teacher that would want the students to give incorrect answers. Moreover, the students certainly have not wrestled in front of the board, nor has the teacher acted as a cruel general. The meaning of this simile should not be taken literally.