The attachment of a muscle tendon to a movable bone or the end opposite the origin.

Correct Answer: A

Rationale: The insertion is the attachment of a muscle tendon to a movable bone, contrasting with the origin, which is attached to a stationary bone. When a muscle contracts, the insertion moves toward the origin, producing motion. For example, in the quadriceps, the insertion on the tibia moves during knee extension. The diaphragm is a specific muscle, not an attachment type. Compartments refer to muscle groups, not individual attachments. Superficial indicates location, not a connection point. The insertion's role as the movable end is a foundational concept in muscle anatomy, making it the correct answer, as it directly corresponds to the definition provided and distinguishes it from the stationary origin.

Correct Answer: B

Rationale: Strabismus is the condition of misaligned eyes (crossed eyes), where eye muscles fail to coordinate, common in young children and treatable with therapy or surgery. The child recognizing people suggests vision is intact, just misaligned. Nystagmus is involuntary eye movement, not crossing. Presbyopia is age-related focus loss, irrelevant here. Myopia is nearsightedness, not alignment-related. Strabismus matches the crossed-eye presentation, making it the correct answer, as it's a muscle coordination issue distinct from refractive or movement disorders, often seen in pediatric cases.

Correct Answer: C

Rationale: Nodding yes involves extension (head tilts back) and flexion (head tilts forward) at the neck, driven by muscles like the sternocleidomastoid and splenius. Rotation and circumduction involve turning or circling, not nodding. Lateral/medial rotation twists the head, not tilting it. Abduction/adduction don't apply to neck nodding. Extension and flexion are the correct actions, as they describe the up-and-down motion, fundamental to neck kinematics in this gesture.

Correct Answer: C

Rationale: The human body contains approximately 640 muscles, a widely accepted estimate in anatomy reflecting skeletal muscles primarily, which vary slightly by individual due to small accessory muscles. This number excludes smooth and cardiac muscles' microscopic units but focuses on distinct, named skeletal muscles enabling movement. Fewer, like 340, undercounts the extensive network across limbs, torso, and face. Higher figures like 860 might exaggerate by including minor variants or non-skeletal types, but 640 aligns with standard texts. It accounts for paired muscles (e.g., biceps) and smaller ones (e.g., in the ear), balancing precision with practicality. This figure underscores the muscular system's complexity, supporting diverse functions from walking to facial expressions, and provides a reliable benchmark for anatomical study, distinguishing it from overly broad or narrow estimates.

Correct Answer: C

Rationale: Cellular respiration encompasses breaking down food (glucose) with oxygen to produce energy (ATP) in cells, mainly via aerobic means in mitochondria, releasing carbon dioxide and water. Anaerobic respiration skips oxygen, yielding less energy and lactic acid. Aerobic respiration is a subset, but cellular respiration covers all energy-making processes, fitting broadly. Oxygen is a reactant, not the process. This oxygen-dependent breakdown fuels most organisms, contrasting anaerobic's limited scope, and its cellular scope includes glycolysis and beyond, making it the precise term for energy formation across living systems.