Answer:
Helper T cells are arguably the most important cells in adaptive immunity, as they are required for almost all adaptive immune responses. They not only help activate B cells to secrete antibodies and macrophages to destroy ingested microbes, but they also help activate cytotoxic T cells to kill infected target cells.
Explanation:
Helper T cells become activated when they are presented with peptide antigens by MHC class II molecules, which are expressed on the surface of antigen-presenting cells (APCs). Once activated, they divide rapidly and secrete cytokines that regulate or assist the immune response.
C.it changes DNA,but it is random
Answer:
A.) Pollen are well preserved in the sediment layers because they are highly resistant to decay.
B.) Other indicators that can be used to determine past climates are through the analysis of the width of tree rings and the coral reefs formed underwater.
your anwer is c) The two types of wings share a common function (and therefore are both called ... the bird wing and insect wing did not arise from an original ancestral structure ... When the gill slits became supported by cartilaginous elements, the first set of
