The correct answer is C. wild.
The word “berserk” means to behave in a wild and uncontrolled way, often as a result of anger or fear. In the context of the question, the horse is described as suddenly going berserk, which means that it started to behave in a wild and uncontrolled way. This could have been caused by a number of things, such as the jockey’s actions, the horse’s environment, or the horse’s own temperament.
The other options are not correct because they do not accurately describe the horse’s behavior. Option A, broke, means to separate into pieces or to become damaged. Option B, galloping, means to ride a horse at a fast speed. Option D, began, means to start or to do something for the first time.
In conclusion, the correct answer to the question “As the jockey tried to ride the horse, it suddenly went berserk.” is C. wild.