A source of hospital-acquired infection could be:

Correct Answer: D

Rationale: The correct answer is D because all the choices can contribute to hospital-acquired infections. New patients in the incubation period can spread infections, medical staff can inadvertently transmit infections, and contaminated medical instruments can also be a source of infections. Therefore, it is important to consider all these factors to prevent and control the spread of infections in a hospital setting.

Correct Answer: D

Rationale: Step-by-step rationale for why answer choice D is correct: 1. Coronaviruses can cause reinfections due to potential waning immunity. 2. Studies have shown cases of reinfections with different strains or within a short period. 3. This contradicts the notion that reinfections cannot be observed. Summary: A: Incorrect because some coronaviruses can cause lower respiratory tract infections. B: Incorrect as coronaviruses can exhibit varied symptomatology including asymptomatic cases. C: Incorrect as some coronaviruses like SARS can lead to severe pneumonia and complications.

Correct Answer: D

Rationale: The correct answer is D, "All of these." Monotrichous bacteria have a single flagellum at one end, amphitrichous have flagella at both ends, and peritrichous have flagella distributed all over the surface. The answer D is correct because it includes all these possibilities based on flagella location. Monotrichous is incorrect as it only refers to a single flagellum, amphitrichous is incorrect as it only refers to flagella at both ends, and peritrichous is incorrect as it only refers to flagella all over the surface. Therefore, the correct answer encompasses all these options.

Correct Answer: B

Rationale: The growth of bacteria is a result of water adsorption because water is essential for various metabolic processes within the bacterial cells, such as nutrient uptake, energy production, and waste removal. Water serves as a medium for chemical reactions to occur and provides structural support to the bacteria. Without sufficient water, bacteria cannot thrive and reproduce. A: Air consumption is incorrect because while bacteria may require oxygen for respiration, it is not the primary factor for their growth. C: Enzyme production is incorrect because enzymes are important for various cellular functions but do not directly influence bacterial growth. D: Radio isotopes are incorrect as they are not essential for bacterial growth and can even be harmful to bacterial cells.

Correct Answer: A

Rationale: Ribosomes are the target for antibiotics as they interfere with protein synthesis in bacteria. Aminoglycosides, tetracyclines, macrolides, and lincosamides all target ribosomes by inhibiting protein synthesis at different stages. Beta-lactam antibiotics target cell wall synthesis, not ribosomes. Antifolate compounds, quinolones, and raspicin target DNA synthesis and replication, not ribosomes. Therefore, the correct answer is A as it includes antibiotics that specifically target ribosomes for inhibiting bacterial protein synthesis.