Which blood type is considered the universal donor for red blood cells?

A. Iron, Magnesium, Zinc, and Copper: These are trace elements present in very small amounts and do not contribute significantly to total body weight.

B. Carbon, Hydrogen, Nitrogen, and Oxygen: These four elements are the major components of biomolecules such as proteins, lipids, carbohydrates, and nucleic acids, making up more than 98% of the human body’s mass.

C. Sodium, Chlorine, Iodine, and Fluorine: These elements are essential electrolytes or trace elements but are present in relatively small quantities and do not account for the bulk of body weight.

D. Calcium, Phosphorus, Potassium, and Sulfur: While these elements are important for bone structure and metabolic functions, they contribute a smaller fraction of total body mass compared to C, H, N, and O.

A. Cardiac muscle: Cardiac muscle is found only in the heart. It contracts involuntarily to pump blood and does not move the skeleton.

B. Smooth muscle: Smooth muscle is located in the walls of internal organs and blood vessels. It controls involuntary movements like peristalsis and vessel constriction, not skeletal movement.

C. Skeletal muscle: Skeletal muscle attaches to bones via tendons and contracts voluntarily to produce movement of the skeleton. It also helps maintain posture and generates heat during activity.

D. Connective tissue: Connective tissue, such as ligaments and tendons, supports and connects structures but does not contract to produce skeletal movement.