Final answer:
Muscles are divided into three main groups: cardiac, skeletal, and smooth muscles.
Step-by-step explanation:
Muscles in the human body are primarily divided into three main groups. The correct answer is: B. 3.
These three main groups are:
1. Skeletal Muscles: These are attached to bones by tendons and are responsible for voluntary movements. Skeletal muscles work in pairs to move bones and joints.
2. Smooth Muscles: Found in the walls of internal organs such as the stomach, intestines, and blood vessels, smooth muscles are involuntary and control functions like digestion and blood vessel constriction.
3. Cardiac Muscles: Exclusive to the heart, cardiac muscles are also involuntary. They contract rhythmically to pump blood throughout the circulatory system.
While there are numerous muscles within each group, the fundamental classification into skeletal, smooth, and cardiac muscles forms the basis for understanding the diverse functions and movements in the human body.