Correct Answer: A

Rationale: The correct answer is A: Bordetella pertussis. This bacterium is known for causing whooping cough due to its ability to produce toxins that damage the respiratory tract, leading to severe coughing fits. Clostridium tetani causes tetanus, Haemophilus influenzae can cause respiratory infections but not whooping cough, and Staphylococcus aureus is more commonly associated with skin infections. Therefore, A is the correct choice based on its specific association with the disease in question.

Correct Answer: C

Rationale: The correct answer is C: adhesion. Adhesion refers to the attachment of microbes to surfaces in or on the body without causing harm. Infections (choice A) occur when microbes invade and multiply in the body, leading to harmful effects. Contamination (choice B) refers to the presence of unwanted or potentially harmful substances, not necessarily microbes. Disease (choice D) is a state of poor health caused by a specific agent, such as microbes, resulting in identifiable symptoms. In this context, adhesion best describes the presence of microbes without causing harm or leading to an infection.

Correct Answer: A

Rationale: Rationale: 1. Unicellular organisms with two layers in cytoplasm = Entamoeba gingivalis. 2. Wide pseudopodia = characteristic of Entamoeba genus. 3. Entamoeba histolytica causes amoebic dysentery, not dental plaque. 4. Trichomonas tenax causes periodontal disease, not dental plaque. 5. Lamblia intestinalis causes giardiasis, not related to dental plaque.

Correct Answer: D

Rationale: Step-by-step rationale: 1. The study results indicate water contamination. 2. Contaminated water poses health risks. 3. Therefore, the correct interpretation is that water is contaminated. Summary: - Choice A is incorrect as safety is not confirmed. - Choice B is too mild given the severity of contamination. - Choice C is also incorrect, as it does not accurately reflect the study findings.

Correct Answer: A

Rationale: The correct answer is A: TRUE. The innate immune system is the body's first line of defense against infections and is always active, providing immediate protection without prior exposure to a specific pathogen. It includes physical barriers, such as skin and mucous membranes, and cellular components like phagocytes and natural killer cells. The innate immune response is nonspecific and rapid, providing a crucial initial defense against pathogens. Choice B is incorrect because the innate immune system is always active, even without any prior exposure to pathogens. Choice C is incorrect because the innate immune system is consistently functioning to protect the body, regardless of the situation. Choice D is incorrect as the correct answer is A.