Bacteriophages are:

Correct Answer: C

Rationale: The correct answer is C: Bacteriophages are viruses that infect bacteria. Firstly, bacteriophages are viruses, not white blood cells or bacteria. They specifically target and infect bacteria, not fungi. This is known as a bacteriophage cycle where the virus injects its genetic material into the bacterial cell to replicate and eventually lyse the cell. This process is specific to bacteria and distinguishes bacteriophages from other microorganisms. Therefore, the correct answer is C as it accurately describes the nature and function of bacteriophages.

Correct Answer: D

Rationale: Interferon delta is not a known type of interferon, making choice D incorrect. Interferon beta is indeed produced by fibroblasts (choice A), interferon alpha by leukocytes (choice B), and interferon gamma by lymphocytes (choice C). Each type of interferon is produced by specific cells in the immune system, contributing to the body's defense against viruses and other pathogens.

Correct Answer: B

Rationale: The correct answer is B because Haemophilus influenzae, Streptococcus pneumoniae, and Neisseria meningitidis are the most common causative agents of bacterial meningitis. Haemophilus influenzae is often seen in children, Streptococcus pneumoniae is the most common in adults, and Neisseria meningitidis is common in adolescents and young adults. Choice A is incorrect because although Streptococcus group B and Listeria monocytogenes can cause meningitis, E. Coli K1 is not a common causative agent. Choice C is incorrect because Staphylococcus aureus and Pseudomonas aeruginosa are not typically associated with bacterial meningitis. Choice D is incorrect as there are known causative agents for bacterial meningitis.

Correct Answer: D

Rationale: The correct answer is D: Terminally. In Clostridium tetani, spores are located at the terminal end of the cell. This positioning helps the spores to be released easily when the cell lyses, aiding in the spread of the bacteria. Paracentrally (A) and centrally (C) would not be as efficient for spore release. Subterminally (B) is also incorrect as the spores are specifically located at the terminal end of the cell, not just near it.

Correct Answer: B

Rationale: The correct answer is B because filoviruses, such as Ebola virus, require investigation in specifically equipped laboratories with high biological protection due to their high pathogenicity and risk of transmission. This is essential for ensuring the safety of researchers and preventing outbreaks. A: This is incorrect as filoviruses are not the most common cause of gastroenteritis; they primarily cause severe hemorrhagic fevers. C: Filoviruses are not widespread; they are typically confined to specific regions during outbreaks. D: Mass immunization is not used for filoviruses as there is no established vaccine for general prophylaxis.