Help please I'm timed!, I'll give brainliest, and a thanks!

How can antibodies "remember" a particular bacterial invader or "antigen" on that invader?

Which part of the neuron below is indicated by the arrow, and what is its function? hormones send chemical signals throughout the body to regulate other body processes. hormones are chemical signals that are sent throughout the body to regulate other body processes. hormones send electrical signals throughout the body to regulate other body processes. hormones are electrical signals that are sent throughout the body to regulate other body processes.

There are only about 250,000 known fossil species. true or false