The half-life of a radioisotope is the amon the symbol 42He, the subscript 2 is the mass number for helium and the superscript 4 is the atomic number for helium.
C. the cell membrane.
the membrane let's things in and out of the cell.
A.
B is wrong since water is not soluble in lipids
<span>D. serotonin</span>
Neurotransmitter are biochemicals and compounds transported from one neuron to another.
Neurons are specialised cells that have dendrites, axons and terminal buttons that sends and receives stimuli from the environment and transduces it into a meaningful information and understand the complexities which the brain now functions.
