The geologic time scale A.
began when life first appeared and ended when humans first appeared.
B.
began when life first appeared and still continues today.
C.
began when Earth formed and ended when humans first appeared.
D.
began when Earth formed and still continues today.

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.