The answer to this question would be: excess fluoride intake
The toothpaste has a high amount of fluoride and will increase the blood fluor level. Excess fluoride intake in children can cause fluorosis which was the brown staining of teeth because fluor is deposited in the growing teeth. Fluorosis can happen in children with <8-year ages.
Answer:
Through simple diffusion, down the concentration gradient.
Explanation:
The phospholipids of the membrane are amphipathic with hydrophillic heads and hydrophobic tails. Other polar molecules cannot go through this hydrophobic interior. Since small uncharged lipids are non polar and hydrohobic, they are able to go through the membrane without the help of transport proteins. Therefore, the last two options can be ruled out because facilitated diffusion includes the use of a protein. Diffusion involves molecules moving down the concentration gradient so the second option can be ruled out.
NREM 3
The correct answer is: Stage 3
I hope that helped! c: