Which of the following is not a feature of antibody? elicits complement activation
cytolytic
opsonin
agglutinates antigen for more efficient phagocytosis
neutralizes microbes and toxins by preventing them from binding their target

before, trains worked using the steam engine. thus, it uses heat so it is crucial to apply heat balance. the steam engine absorbs energy during the stage of boiling water. so, this is the endothermic reaction. when the steam is used to work the piston, it has to release this energy through running the train. the excess energy is released as an exhaust to the chimney. this is the exothermic process because it releases energy to the surroundings.

i think the answer is a.keratin is the pigment responsible for skin color.