Which muscle extends the forearm?

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: C

Rationale: The vomer, a midline bone, forms the lower nasal septum, separating the nostrils, and is visible inferiorly at the skull's base, posterior to the maxillae. The mandible is the jaw, not septal. Maxillae form the upper septum and palate, not the lower part alone. The hyoid is in the neck, not the skull. The vomer's plowshare shape and basal visibility, seen in inferior skull views, make 'c' the correct bone.

Correct Answer: B

Rationale: Puberty in females begins with thelarche, the development of breast buds, typically at ages 10-11. Triggered by rising estrogen from ovarian activation via gonadotropins (FSH, LH) from the pituitary, it marks the start of secondary sexual characteristics. Breast budding often appears unilaterally first, reflecting hormonal sensitivity in mammary tissue. Menarche, the first menstrual period, follows 2-3 years later, around 12-13, after significant growth and hormonal maturation, peaking before menstruation starts. Pubarche, pubic hair growth, and adrenarche, adrenal androgen increase, occur later, driven by adrenal and ovarian androgens, not initial puberty onset. Thelarche's precedence reflects the hypothalamic-pituitary-ovarian axis activating earlier than adrenal changes. Puberty spans years, completing by 15-17, with thelarche as the visible starting point, followed by growth spurts and reproductive capability. Pediatric endocrinology data confirm this sequence, distinguishing thelarche from later milestones like menarche, which depends on established ovarian cycles, highlighting its role as puberty's initial physical sign.

Correct Answer: B

Rationale: Pseudostratified columnar epithelium, appearing layered but single-layered with cilia, is typically in the respiratory tract (e.g., trachea), where it secretes mucus and moves debris via ciliary action. Skin has stratified squamous for protection. Stomach lining uses simple columnar for secretion/absorption. Kidney tubules feature simple cuboidal. The respiratory tract's need for mucus trapping and clearance, per tissue distribution, makes 'b' the correct location.

Correct Answer: D

Rationale: Hair's primary functions include all listed: UV protection (scalp shielding), sensory reception (via nerve endings at follicles), and insulation (trapping air for warmth), varying by location (e.g., scalp vs. eyebrows). No single role overshadows others universally scalp hair insulates, eyelashes protect, all sense. This multifunctionality, per hair's evolutionary roles, makes 'd' the correct answer.