The diversity among human antigen receptors is attributed mainly to ________
a. structural changes that occur to antibodies after antibodies meet antigens
b. random splicing of antigen receptor gene segments
c. all of the choices
d. large numbers of genes for antibodies
b
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Humans become infected with the malarial parasite when mosquitoes inject ________ into the bloodstream.
A. sporozoites B. schizonts C. merozoites D. trophozoites
What is an ecological niche?
What will be an ideal response?
In a muscle organ like the biceps muscle,
A. the entire muscle is stimulated at the same time. B. several nerve fibers enter the muscle and each stimulates specific muscle cells. C. several nerve fibers enter the muscle, but each fiber stimulates most of the cells in the muscle. D. there are two or three motor units.
Along coastlines, the area between high tide and low tide is the
A. hydrothermal vent. B. continental shelf. C. intertidal zone. D. estuary. E. open ocean.