Correct Answer: D

Rationale: The correct answer is D: Innate immunity (natural resistance). Innate immunity refers to the non-specific defense mechanisms that act against a variety of infectious agents. This includes physical barriers like skin and mucous membranes, as well as cellular components like phagocytes and natural killer cells. Adaptive immunity (A) is specific and involves the production of antibodies and immune memory (B), which are not part of the initial non-specific response. Antibodies (C) are part of the adaptive immune response and are produced in response to specific pathogens, not part of the non-specific innate defense factors.

Correct Answer: A

Rationale: Rationale for Correct Answer A (Diphtheria): 1. Thin yellow bacilli with dark brown grains on ends suggest Corynebacterium diphtheriae, characteristic of diphtheria. 2. Roman numeral five shape is typical of diphtheria bacilli. 3. Diphtheria causes sore throat and can spread in boarding schools. 4. Neisser staining method is used for diphtheria bacilli. Summary of Incorrect Choices: B: Scarlet fever is caused by Streptococcus pyogenes and presents with rash, not yellow bacilli. C: Listeriosis is caused by Listeria monocytogenes, not consistent with the described findings. D: Tonsillitis can be caused by various bacteria or viruses, but the specific characteristics described do not match.

Correct Answer: D

Rationale: The correct answer is D (All of the above) because all three bacteria (Clostridium botulinum, Escherichia coli, Salmonella enterica) are known to cause foodborne infections. Clostridium botulinum can lead to botulism, E. coli can cause various gastrointestinal illnesses, and Salmonella enterica is a common cause of food poisoning. Each bacterium has specific mechanisms that result in foodborne illnesses. Choices A, B, and C are incorrect because each bacterium mentioned is associated with causing foodborne infections, making them collectively the correct answer.

Correct Answer: C

Rationale: Rationale: Choice C is correct because immunomodulators can indeed be natural (e.g., cytokines) or artificial compounds (e.g., synthetic peptides). They work by modulating the immune response, enhancing or suppressing it as needed. Choice A is incorrect because immunomodulators can stimulate both humoral and cellular immune responses. Choice B is incorrect as isoniazid is primarily an antibiotic used to treat tuberculosis, not an immunomodulator. Choice D is incorrect because immunomodulators can have varying effects on the immune response, not just suppress it.

Correct Answer: A

Rationale: Osmosis is the correct answer because it is the process by which water molecules move across a semi-permeable membrane from an area of low solute concentration to an area of high solute concentration. This movement occurs passively, driven by the concentration gradient. Facilitated diffusion (B) involves the transport of specific molecules with the help of carrier proteins, not water. Phagocytosis (C) is a process where cells engulf solid particles, not water molecules. Exocytosis (D) is the process of releasing substances from a cell by fusion of vesicles with the cell membrane, not the transport of water across the membrane.