The space between the ribs is filled with:

Correct Answer: A

Rationale: Intercostal muscles external, internal, innermost fill spaces between ribs, aiding breathing by elevating or depressing the ribcage. Costal cartilage connects ribs to the sternum, 'intercostal space' is the gap they occupy, and pleura lines the chest cavity. These striated, voluntary muscles distinguish the intercostal region's role in respiration, key to thoracic mechanics, contrasting with cartilage or membrane functions.

Correct Answer: D

Rationale: Contraction shortens sarcomeres myofibril segments via actin-myosin sliding, reducing Z-line distance. Fascicles (fibre bundles) shorten collectively, but actin and myosin molecules don't; filaments overlap. Sarcomeres' shortening distinguishes them as the contractile unit, summing to muscle movement.

Correct Answer: D

Rationale: Extensor digitorum extends fingers, gluteus minimus abducts the hip, and biceps femoris flexes the knee all are real, logical names based on action, location, or shape. 'Extensor minimus longus' is nonsensical: 'minimus' (smallest) and 'longus' (long) contradict, and no such muscle exists in standard nomenclature. Extensors typically specify a region (e.g., digitorum), and 'minimus' pairs with size (e.g., gluteus), not length. This fabricated name's inconsistency makes 'd' the correct choice.

Correct Answer: B

Rationale: The triceps brachii extends the forearm, straightening the elbow by contracting its three heads, originating from scapula/humerus and inserting on the ulna. Biceps brachii flexes the elbow. Brachialis also flexes, beneath biceps. Deltoid moves the shoulder, not forearm. Triceps' role as the primary elbow extensor, opposing biceps, makes 'b' the correct muscle.

Correct Answer: A

Rationale: The lambdoid suture, a jagged seam at the skull's posterior, is formed by the articulation of the occipital bone (base/back) and the parietal bones (top/sides), resembling a lambda (Λ) shape. Parietal and temporal bones meet at the squamous suture, not lambdoid. Parietal and frontal bones form the coronal suture anteriorly. Occipital and temporal bones connect at the occipitomastoid suture, not lambdoid. The lambdoid's distinct occipital-parietal junction, visible in skull models, confirms 'a' as the correct pairing.