Which of the following statements is correct about what happens during flexion?

Correct Answer: B

Rationale: Flexion decreases the angle between bones, as in bending the elbow (humerus and radius/ulna), bringing bones closer via flexor muscles like biceps. Increasing the angle occurs in extension, the opposite motion. Moving away from the body describes abduction, not flexion, which is joint-specific. Moving toward the body's center could fit some flexions (e.g., hip), but it's less universal than angle decrease, which defines flexion across joints like elbow, knee, or neck, distinguishing it from extension, lateral, or midline motions.

Correct Answer: D

Rationale: Sartorius, a long, strap-like muscle, flexes, abducts, and laterally rotates the hip, then flexes the knee, enabling leg crossing. Gluteus maximus extends the hip. Piriformis rotates it. Gracilis adducts, not crossing fully. Sartorius' multi-joint action distinguishes it, critical for this coordinated motion.

Correct Answer: C

Rationale: Intestinal symptoms like diarrhea, vomiting, and abdominal pain stem from toxins disrupting gut function. Enterotoxins, produced by bacteria such as Escherichia coli or Staphylococcus aureus, target intestinal cells, increasing secretion or reducing absorption by altering ion channels or tight junctions, as seen in cholera. Cytotoxins cause broader cell damage, not specific to the gut. Neurotoxins affect nerves, not digestion directly. Leukocidins attack immune cells, not intestinal ones. Enterotoxins' specific action on gut epithelium, leading to fluid loss and characteristic symptoms, distinguishes them as the cause, critical for diagnosing gastrointestinal bacterial infections.

Correct Answer: A

Rationale: Cellular respiration encompasses the breakdown of glucose to produce ATP, involving glycolysis, the Krebs cycle, and the electron transport chain. Glycolysis includes anaerobic glucose splitting, yielding pyruvate, which feeds the Krebs cycle under aerobic conditions. The Krebs cycle generates electron carriers, fueling the electron transport chain for ATP synthesis. Anaerobic splitting is a subset when oxygen is absent. Cellular respiration's integration of these stages, converting food to energy, makes it the overarching process, central to cellular metabolism across organisms.

Correct Answer: C

Rationale: Most bacteria thrive at 37°C (98.6°F), mimicking human body temperature, ideal for pathogens like E. coli in lab cultures. An incubator maintains this stable warmth, promoting growth. A lighted window (22°C) varies and is cooler, a refrigerator (7°C) slows metabolism, and a freezer (-12°C) halts it. The incubator's optimal temperature, matching bacterial physiology, ensures rapid division and colony formation, making it the best choice for cultivating diverse species.