What property of water allows someone to fill a glass slightly above the rim without the water flowing over?

Correct Answer: D

Rationale: Water's ability to mound above a glass rim results from surface tension, a property arising from cohesive forces between its molecules. Hydrogen bonds create a strong, elastic 'skin' at the surface, resisting external disruption and allowing water to hold together against gravity briefly. Specific gravity relates to density, not this behavior. Cohesion contributes but isn't the complete mechanism. Opacity, transparency-related, is irrelevant. Surface tension's role in forming this temporary barrier, driven by molecular attraction, explains the phenomenon, a key feature in water's physical behavior.

Correct Answer: A

Rationale: The kidney filters blood and regulates fluid balance primarily through nephrons microscopic units numbering millions per kidney. Each nephron's glomerulus filters plasma, while tubules reabsorb water, glucose, and ions, and excrete waste as urine. Neurons conduct signals, ureters transport urine, and alveoli exchange lung gases. The nephron's integrated filtration, reabsorption, and secretion, occurring in structures like the loop of Henle, perform the kidney's core work, maintaining homeostasis and distinguishing it as the functional powerhouse.

Correct Answer: D

Rationale: Thin filaments comprise actin (structural backbone), troponin (Ca²⁺-binding regulator), and tropomyosin (site-covering protein), interacting with myosin for contraction. Myosin forms thick filaments, excluded from thin ones. Listing only troponin or tropomyosin omits actin's essential role thin filaments need all three. Actin alone misses regulatory components. The combination minus myosin defines thin filaments, enabling controlled actin-myosin binding, distinguishing it from partial or thick filament compositions, critical for sarcomere function.

Correct Answer: A

Rationale: Muscle cell components have specialized roles. The sarcolemma is the plasma membrane, sarcoplasm the cytoplasm, and sarcoplasmic reticulum a calcium-storing organelle all integral to muscle function. Sarcoma, however, denotes a connective tissue cancer, not a cellular structure, unrelated to normal muscle anatomy. This distinction matters: muscle-specific terms prefix sarco for flesh, but sarcoma's pathological context excludes it from healthy cell anatomy, unlike the others, which enable contraction and signal transduction in skeletal muscle fibres.

Correct Answer: A

Rationale: Muscle fibres contain hierarchical structures. Myofibrils, bundles of sarcomeres, span the fibre's length (tens to hundreds of micrometres), housing myofilaments actin and myosin arrays within sarcomeres. Myosin is a protein molecule, and myopic is unrelated (likely a typo). Myofibrils, as the largest organized unit within the cell, integrate sarcomeres for contraction, distinguishing them from shorter myofilaments or molecular components, critical for muscle's macroscopic force generation.