Why is smallpox considered a factor that greatly helped European explorers to defeat the Native populations of the Americas (e.g. Mexico)?

Correct Answer: C

Rationale: The correct answer is C because smallpox was indeed introduced to the Americas by European explorers, leading to devastating effects on the Native populations who had no immunity. This weakened the Natives' ability to fight back against the Europeans. Option A is incorrect as there was no ongoing smallpox epidemic in the Americas before the arrival of the Europeans. Option B is also incorrect as there is no evidence that the Native populations used a lethal form of vaccination against smallpox. Option D is incorrect as only option C accurately explains the impact of smallpox on the Native populations in relation to European conquest.

Correct Answer: C

Rationale: The correct answer is C: CARD. CARD stands for Caspase Activation and Recruitment Domain, which is crucial for the assembly of the inflammasome complex. It facilitates the recruitment and activation of caspase enzymes, leading to inflammatory responses. Leucine rich repeats (A) and TIR domain (B) are not directly involved in the assembly of the inflammasome. Therefore, the correct choice is C, as it specifically pertains to the structural domain essential for this process.

Correct Answer: B

Rationale: The correct answer is B because the statement is false. Memory B cells are formed during an immune response and persist long-term, allowing for a faster and more robust response upon reinfection with the same antigen. The number of memory B cells recognizing an antigen is typically greater than the number of naïve B cells, as they are specifically primed and preserved. In contrast, naïve B cells are naive to the antigen and need to undergo activation and differentiation upon encountering the antigen for the first time. Therefore, statement B is incorrect as it inaccurately suggests that memory B cells are always fewer than naïve B cells recognizing the same antigen.

Correct Answer: C

Rationale: The correct answer is C because both external barriers (Skin, Secretions, Mucous membranes) and internal defenses (Inflammatory response) are types of innate immunity. External barriers physically block pathogens from entering the body, while internal defenses involve cellular and molecular responses to eliminate pathogens. Choice A alone does not cover internal defenses, and choice B alone does not cover external barriers, making them individually incomplete. Choice D is incorrect as innate immunity does involve specific barriers and responses. Therefore, choice C is the best answer as it encompasses both types of innate immunity barriers.

Correct Answer: D

Rationale: The correct answer is D because anemia is defined as having abnormally low amounts of hemoglobin or red blood cells, leading to reduced oxygen-carrying capacity. This results in symptoms such as fatigue and weakness. Choice A is incorrect because anemia is not related to cancer of white blood cells. Choice B is incorrect as anemia does not result in extra leukocytes; rather, it leads to a decrease in red blood cells. Choice C is incorrect as anemia is not usually fatal if treated promptly and effectively.