Which type of burn affects only the epidermis?

Correct Answer: A

Rationale: First-degree burns affect only the epidermis, causing redness and pain (e.g., sunburn), without deeper damage. Second-degree reaches the dermis, blistering. Third-degree destroys both layers, numbing nerves. Fourth-degree extends to muscle/bone, rare. Epidermal-only involvement, per burn classification, makes 'a' correct.

Correct Answer: D

Rationale: Ribs (1-12) include true (1-7, direct sternal attachment) and false (8-12, indirect or none), forming the cage. Sternum connects ribs, thoracic vertebrae anchor them, costal cartilage links true ribs none encompass both types. Ribs' classification, per thorax, makes 'd' correct.

Correct Answer: B

Rationale: The knee joint, or femorotibial joint, is between the femur and tibia, a hinge for leg movement. Humeroulnar is elbow, coxofemoral is hip, talocrural is ankle. Femorotibial's specificity, per joint nomenclature, makes 'b' correct.

Correct Answer: A

Rationale: An organ, like the stomach, is a collection of similar tissues (e.g., muscle, epithelium) working together for a specific function (digestion). An organelle is a cellular structure (e.g., mitochondria), not tissues. An organism is the whole living entity. An organ system like the digestive system includes multiple organs, broader than one. The organ's tissue-based, functional unity, per anatomical hierarchy, makes 'a' correct.

Correct Answer: B

Rationale: Childbirth uses a positive feedback loop: uterine contractions increase oxytocin, intensifying contractions until delivery, amplifying the stimulus. Blood pressure , fluid balance , and temperature use negative feedback to stabilize. Positive feedback's escalating nature in labor, per physiology, makes 'b' correct.