Opsonization of pathogens by both antibodies and complement proteins (C3b) leads to uptake and destruction of the pathogen by phagocytic cells that express both Fc receptors and complement receptors. Which of the following in Figure Q2.16 is the most efficient form of dual opsonization of the pathogen by antibody and C3b to maximize phagocytosis?

Correct Answer: A

Rationale: Assuming Q2.16 shows options, dual opsonization with IgG and C3b maximizes phagocytosis via Fc and complement receptors.

Correct Answer: D

Rationale: Auxins promote seedling elongation, are transported downward (polar transport), and affect root elongation at lower concentrations. All options are correct.

Correct Answer: D

Rationale: The lymphatic system returns interstitial fluid to blood and combats infections via lymph nodes and organs, not coagulation or hormone production.

Correct Answer: A

Rationale: Interleukin-2, from helper T cells, promotes T cell proliferation, not mast cell histamine release, APC stimulation, or macrophage phagocytosis.

Correct Answer: C

Rationale: C3b coats pathogens to enhance phagocytosis (opsonization), while antibodies also opsonize, but surfactants do not; C3b is the most specific example here.