Activated c3b to the cell wall of an infected cell or pathogen is the end-result of which of the following pathway(s)?

Correct Answer: D

Rationale: The correct answer is D because all three pathways (classical, lectin, and alternative) converge at the point of C3 activation, leading to the formation of C3b that binds to the cell wall of an infected cell or pathogen. In the classical pathway, C3 is activated by C4b2a complex; in the lectin pathway, it is activated by mannose-binding lectin-associated serine proteases; and in the alternative pathway, it is activated by spontaneous hydrolysis of C3. Therefore, the end result of all three pathways is the activation of C3 and subsequent binding of C3b to the cell wall. Choices A, B, and C are incorrect because each pathway alone does not lead to the activation of C3b and binding to the cell wall; it is the combined action of all three pathways that achieves this end result.

Correct Answer: B

Rationale: Low pH (acidic conditions) causes hemoglobin to release oxygen more readily, enhancing oxygen delivery to tissues during internal respiration. External respiration (A) involves gas exchange in the lungs, not affected by pH. Carbon dioxide transport (C) is influenced by pH, but not directly related to oxygen binding. Hemoglobin synthesis (D) is the production of hemoglobin molecules, not influenced by pH during oxygen binding. Therefore, the correct answer is B as low pH primarily affects oxygen release during internal respiration.

Correct Answer: D

Rationale: The correct answer is D: sudden infant death syndrome (SIDS). SIDS is the leading cause of death for children under 1 year old due to unexplained reasons, typically occurring during sleep. A: Motor vehicle accidents are more common in older children. B: Falls are also more common in toddlers who are more mobile. C: Cardiac congenital malformations are a significant cause of death but are not the leading cause in this age group.

Correct Answer: B

Rationale: The correct answer is B: Persistent coughing. In heart failure, fluid may accumulate in the lungs, leading to a persistent cough. High blood pressure (A) is a risk factor for heart failure but not a symptom. Excessive weight loss (C) is not a typical symptom of heart failure; instead, patients may experience weight gain due to fluid retention. Increased energy levels (D) are unlikely in heart failure, as fatigue and weakness are common symptoms. Therefore, the most common symptom of heart failure among the choices given is persistent coughing.

Correct Answer: B

Rationale: The correct answer is B: Tidal volume. Tidal volume is the amount of air normally inhaled or exhaled with one normal breath. It represents the typical volume of air moved in and out of the lungs during normal breathing. The other choices are incorrect because: A) Expiratory reserve volume is the additional amount of air that can be exhaled after a normal exhalation; C) Residual volume is the volume of air remaining in the lungs after a maximum exhalation; D) Total lung capacity is the sum of all lung volumes, including tidal volume, inspiratory reserve volume, expiratory reserve volume, and residual volume.