Factors important in the eradication of smallpox include

Correct Answer: D

Rationale: The correct answer is D because all the factors mentioned are important in the eradication of smallpox. A is correct because smallpox is specific to humans, simplifying eradication efforts. B is correct as the vaccine was easily deployable. C is correct as isolation of symptomatic individuals helped control the spread. Therefore, all choices are important in the successful eradication of smallpox.

Correct Answer: D

Rationale: Neutrophils lack the ability to present antigens to T cells due to their short lifespan and absence of major histocompatibility complex (MHC) class II molecules. This process requires MHC class II presentation, which is typically done by antigen-presenting cells such as dendritic cells, macrophages, and B cells. Neutrophils primarily function in phagocytosis, releasing reactive oxygen species (ROS), defensins, and neutrophil extracellular traps (NETs) to combat pathogens. Thus, the correct answer is D. Other choices are incorrect because neutrophils are capable of producing ROS (A), defensins (B), and NETs (C).

Correct Answer: B

Rationale: Rationale for Answer B: 1. Antibody structure consists of two identical heavy chains and two identical light chains. 2. These chains are covalently linked to form the Y-shaped structure of an antibody. 3. Each chain contributes to the formation of antigen-binding sites. 4. Therefore, two identical heavy chains and two identical light chains form two antigen-binding sites. Summary of Incorrect Choices: A: Incorrect because it describes only one antigen-binding site formed by one light chain and one heavy chain. C: Incorrect because it describes one antigen-binding site formed by two identical heavy chains and two identical light chains. D: Incorrect because it incorrectly describes the roles of light and heavy chains in antibody structure.

Correct Answer: C

Rationale: The correct answer is C: Ethylene. Ethylene is indeed a gaseous plant hormone produced during the combustion of natural gas. It plays a crucial role in various plant processes such as fruit ripening, senescence, and stress responses. A: Auxin is not a gaseous hormone and is primarily involved in promoting cell elongation and root growth. B: Gibberellins are not gaseous hormones and mainly regulate plant growth processes like stem elongation and seed germination. D: The statement "All above" is incorrect as auxin and gibberellins are not gaseous hormones, only ethylene fits the description. Therefore, choice C, Ethylene, is the correct answer as it is the gaseous by-product of natural gas combustion and a plant hormone.

Correct Answer: D

Rationale: The correct answer is D: All above. The vibrations from sound waves are amplified by the eardrum, Anvil (also known as the Incus), and Stirrup (also known as the Stapes), which are the three tiny bones in the middle ear. The sound waves travel through the ear canal and hit the eardrum, causing it to vibrate. The vibration is then transmitted through the Anvil to the Stirrup, which amplifies the vibrations and sends them to the inner ear. Each of these three components plays a crucial role in the process of amplifying sound vibrations for better auditory perception. Therefore, all three choices are correct in this context.