The correct answer is option 1: Bacillus. Bacillus refers to a type of bacterial shape characterized by a rod-like or cylindrical form. Mycobacterium leprae, the bacterium responsible for causing leprosy, belongs to the Bacillus category. This means that the bacterium is shaped like a rod. It is important to note that Mycobacterium leprae is a pathogenic bacterium, meaning it can cause disease in humans. It primarily affects the skin and peripheral nerves, leading to symptoms such as skin lesions and nerve damage. It is transmitted through close and prolonged contact with an infected individual. Effective treatment for leprosy is available, and early diagnosis and treatment can prevent severe complications.