D .............. im pretty sure its this one :)
Answer:
Carbon dioxide moves in; oxygen moves out
Explanation:
"They contain at least one double or triple bond" is true of saturated fatty acid chains. This extra bond is why they are called "saturated", because they had less ability to take on other bonds.
Answer:
C
Explanation:
To send signals to the blood vessels to constrict or dilate , to increase or decrease blood flow respectively.
There has to be one side with a high concentration and another side with a lower concentration
