Answer:
peptide antigens by MHC class II molecules
Explanation:
Helper T cells are activated by peptide antigens by MHC class II molecules. These antigens express on the surface of antigen-presenting cells (APCs). After activation, the T helper cells divide and secrete cytokines to assist the immune response.
Answer: A because two of the same pairs are homologous
A carbon atom can form a maximum of 4 single covalent bonds
A. Hormones
secreted directly into the blood
When a glacier melts, the ocean level rises therefore causing flooding and creating alien environments for those species that either live near the glaciers or on them.