Correct Answer: B

Rationale: The correct answer is B: Outer membrane with lipopolysaccharides. Gram-negative bacteria have an outer membrane containing lipopolysaccharides (LPS), which are important in pathogenesis and immune response. This feature is unique to Gram-negative bacteria, distinguishing them from Gram-positive bacteria (choice A). Teichoic acids (choice C) are found in the cell walls of Gram-positive bacteria, not Gram-negative. The statement in choice D, absence of a cell wall, is incorrect as all bacteria have a cell wall, although the composition may vary between Gram-negative and Gram-positive bacteria.

Correct Answer: B

Rationale: The Gram stain differentiates bacteria based on cell wall structure. It classifies bacteria into Gram-positive (purple) and Gram-negative (pink) based on the presence of peptidoglycan in the cell wall. This method helps in identifying the bacterial species and determining appropriate treatment. Option A (Cell shape) is incorrect because the Gram stain focuses on cell wall composition, not cell shape. Option C (Flagella composition) is incorrect as the Gram stain does not assess flagella. Option D (Nutrient requirements) is incorrect as it does not relate to the purpose of the Gram stain.

Correct Answer: B

Rationale: The correct answer is B: Inactivation. In this method, the sputum sample is processed with a solution of caustic soda, which helps to kill any contaminants present and preserve the tuberculosis bacillus for microscopic examination. This step is crucial in ensuring accurate detection of the bacillus. A: Homogenization involves breaking down the sample to make it uniform, but it does not necessarily involve using caustic soda for inactivation. C: Flotation is a method used to separate different components based on their density and is not specific to inactivating tuberculosis bacillus. D: Filtration involves passing a sample through a filter to separate particles based on size and is not related to inactivating the tuberculosis bacillus.

Correct Answer: A

Rationale: The correct answer is A: cytomegalovirus. CMV is the most common virus transmitted during pregnancy, leading to potential serious complications for the fetus. It can cause birth defects, hearing loss, and developmental delays. CMV is commonly spread through bodily fluids. HIV (B) can also be transmitted during pregnancy but is less common. Herpes simplex virus (C) can be transmitted but typically results in localized infection. Epstein-Barr virus (D) is not commonly transmitted during pregnancy.

Correct Answer: D

Rationale: The correct answer is D: epidermolytic toxin. This toxin specifically targets the epidermis, leading to exfoliation seen in scalded skin syndrome (SSS). Hemolysis (A) refers to the destruction of red blood cells, not relevant to SSS. Enterotoxins (B) cause food poisoning, not SSS. Leucocidins (C) target white blood cells, not pertinent to SSS. Therefore, the epidermolytic toxin (D) is the correct choice for causing SSS.