Answer:
B
Explanation:
About 54O mil years ago the Camberian Explosion happened and in Camberian period major animal phyla appear according to fossil records.
Activated cytotoxic cells (t lymphocytes) flags cells for destruction by macrophages. Ctotoxic t cells are the most important cells in the adaptive immunity, since they are required for almost all adaptive immune responses. They help activate B cells to secrete abtibodies and macrophages to destroy ingested microbes and also activate cytotoxic t cells to kill infected target cells.
Answer:
The grasshopper doesn't have to use it circulatory system to carry gases to and from the grasshopper cells because the air that is passed through the trachea system is already close enough to get to the cells.
Explanation:
"In the grasshopper, exchange of oxygen and carbon dioxide occurs in the tracheal system. Hemolymph plays no part in the process. There is not even an oxygen-carrying pigment in insect hemolymph." - www.biology-pages.info
(Here's some extra info as well)