The answer is the letter B. Electrical signals.
*Our brain and body communicates with each other by sending messages in the form of electrical signals.
<span>LD
means lethal dose. LD50 is the amount of a material, administered at once to
cause the death of half (50%) of a group of test organisms. A test which shows that LD50 of a certain
chemical is 20 mg per kg means that 20 milligrams of that chemical for every 1
kilogram body weight of the test animal when administered in one dose, causes
the death of 50% of the test group.</span>
Answer:
The cell membrane is permeable to small solutes to let them easily diffuse in and out of the cells.
The brain and the skull the skull protects the brain
