The adaptive immune response:

Correct Answer: D

Rationale: The correct answer is D because the adaptive immune response relies on the initiation by the innate immune response (A), involves both humoral (antibody production) and cell-mediated (T cell activation) responses (B), and produces cytokines that can modulate the activity of innate immune cells like macrophages (C). Therefore, all of the statements are true regarding the adaptive immune response, making option D the correct choice.

Correct Answer: C

Rationale: The correct answer is C: Peptidoglycan. NOD1 recognizes peptidoglycan, a component of bacterial cell walls. This recognition triggers an immune response. Flagellin (A) is recognized by TLR5, CpG DNA (B) is recognized by TLR9, and K+ efflux (D) is not a PAMP recognized by NOD1. Thus, only peptidoglycan is the correct choice for NOD1 recognition.

Correct Answer: C

Rationale: The correct answer is C because the C3 convertase is an enzyme that cleaves C3 into C3a and C3b, an essential step in the complement cascade. This enzyme is crucial for the initiation of both the classical and alternative pathways. Choice A is incorrect as opsonins enhance phagocytosis but are not directly related to C3 convertase. Choice B is incorrect as the MAC is formed by the terminal complement components, not the C3 convertase. Choice D is incorrect as C3b is not an inhibitor but a product of C3 cleavage by the C3 convertase.

Correct Answer: A

Rationale: The correct answer is A because innate behaviors are indeed under strong genetic control. These behaviors are instinctual and are genetically programmed in organisms. This genetic control ensures that all individuals of a species exhibit these behaviors consistently. Choice B is incorrect because while innate behaviors may be performed similarly by individuals of a species, there can still be variations. Choice C, Sociobiology, is incorrect as it is a branch of biology that studies social behavior in animals. Choice D, the environment, is incorrect as innate behaviors are not primarily influenced by the environment but rather by genetic factors.

Correct Answer: A

Rationale: The correct answer is A: a general receptor. Blood type AB individuals have both A and B antigens on their red blood cells, making them universal recipients since they can receive blood from all blood types without rejection. This is because they have no antibodies against A or B antigens. The other choices are incorrect because blood type AB individuals cannot be universal donors (choice B) as they have both A and B antigens, not making them suitable for all recipients. They are not both a receptor and donor (choice C) as they can only receive blood from all types, not donate to all. Lastly, they are not neither donating nor a receptor (choice D) since they can receive blood from all types, making them a receptor.