The five metacarpals, which make up the palm of the hand and connect to the phalanges, are named one through five from ... .

Correct Answer: B

Rationale: Metacarpals are numbered 1 to 5 from thumb (lateral) to pinky (medial) in anatomical position, aligning with phalange numbering and standard convention.

Correct Answer: B

Rationale: An adult human typically has 12 pairs of ribs (24 total): 7 true pairs (attaching to the sternum), 3 false pairs (indirectly attached), and 2 floating pairs (no sternal attachment). 10 undercounts, while 14 and 16 exceed the standard anatomical count.

Correct Answer: C

Rationale: Flat bones, like the scapula (shoulder blade) and cranial bones, are thin and broad, providing a protective barrier for internal organs. The cranial bones protect the brain, while the scapula contributes to the shoulder structure, indirectly aiding in upper body protection. Although flat bones like those in the skull and sternum also produce blood cells in their marrow, their primary function is protection, making 'Protect internal organs' the correct answer.

Correct Answer: B

Rationale: Long bones are characterized by a cylindrical shape, with a shaft (diaphysis) and ends (epiphyses), and are primarily found in the limbs (e.g., femur, humerus). Short bones are cube-shaped (e.g., carpals), irregular bones have complex shapes (e.g., vertebrae), and flat bones are broad and thin (e.g., scapula), making 'Long bone' the correct answer.

Correct Answer: C

Rationale: Acetylcholine (ACh) is the neurotransmitter released by motor neurons into the synaptic cleft at the neuromuscular junction. It binds to receptors on the muscle fiber, initiating an action potential that leads to contraction. Serotonin, GABA, and dopamine have other neural roles, making 'Acetylcholine (ACh)' the correct answer.