Correct Answer: B

Rationale: The correct answer is B: Helicobacter pylori. This bacterium is known to be the primary cause of peptic ulcers by colonizing the stomach lining and causing inflammation. It produces urease enzyme to neutralize stomach acid and has a flagellum for mobility. Escherichia coli (A) is mainly associated with foodborne illnesses. Streptococcus pyogenes (C) causes strep throat and skin infections. Mycobacterium tuberculosis (D) causes tuberculosis, a respiratory infection. Therefore, Helicobacter pylori is the correct choice for peptic ulcers based on its unique characteristics and pathogenicity.

Correct Answer: C

Rationale: The correct answer is C: Tubular filtration. The kidney does not perform tubular filtration as a method for urine formation and drug clearance. The process of urine formation involves filtration, secretion, and reabsorption. Filtration occurs at the glomerulus, where blood is filtered to form the initial filtrate. Tubular secretion involves the active transport of substances from the blood into the renal tubules to be eliminated in urine. Tubular reabsorption is the process of reclaiming useful substances from the filtrate back into the blood. Therefore, tubular filtration is not a valid process in urine formation and drug clearance, making it the correct answer. Choices A, B, and D are incorrect as they are essential processes in urine formation and drug clearance.

Correct Answer: A

Rationale: Step 1: Bordetella pertussis is the causative agent of whooping cough, also known as pertussis. Step 2: This bacterium produces toxins that damage the respiratory tract, leading to severe coughing fits. Step 3: Clostridium tetani causes tetanus, Haemophilus influenzae causes respiratory infections, and Staphylococcus aureus causes skin infections. Step 4: Therefore, A is the correct answer as it is the only bacterium directly associated with whooping cough.

Correct Answer: A

Rationale: The correct answer is A because most bacteria can grow in both the presence and absence of oxygen. Some bacteria are aerobic and require oxygen for growth, while others are anaerobic and can grow in the absence of oxygen. Choice B is incorrect because not all bacteria grow in the absence of oxygen. Choice C is incorrect because not all bacteria are microaerophiles, which are bacteria that require a low level of oxygen for growth. Choice D is incorrect because most bacteria exhibit flexibility in their oxygen requirements.

Correct Answer: A

Rationale: The correct answer is A: Vibrio cholerae. This bacterium produces cholera toxin, an exotoxin that causes severe dehydration and diarrhea by increasing the secretion of electrolytes and water in the intestines. Vibrio cholerae is the causative agent of cholera, a disease characterized by profuse watery diarrhea. Choice B, Clostridium tetani, produces tetanospasmin causing tetanus, not dehydration or diarrhea. Choice C, Escherichia coli, can cause diarrhea but rarely severe dehydration. Choice D, Shigella dysenteriae, produces Shiga toxin leading to bloody diarrhea, not severe dehydration.