Final answer:
The scalene muscles are responsible for flexing and rotating the neck.
Step-by-step explanation:
The group of muscles that work together to flex, laterally flex, and rotate the neck are the scalene muscles. These include the anterior scalene muscle, which is located anterior to the middle scalene, the middle scalene muscle, which is the longest and lies intermediate between the anterior and posterior scalenes, and the posterior scalene muscle, which is the smallest and sits posterior to the middle scalene. These muscles are significant not only for their role in neck movement but also contribute to deep inhalation.