Answer:
A group of cells make a tissue, a group of tissues make and organ, a group of organs make an organ system, and an organ system makes a organism.
Skin cells are made of proteins, water, and fat. But brain cells are only made up of amino acids, which ca make protein.<span />
Answer:
both options 4 and 3 is the answer..
Most of the brain's excitatory ionotropic synapses use the neurotransmitter glutamate.
The best correct answer is C.
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