Adaptation is the correct answer
Answer:
B (active transport using ATP)
Explanation:
Movement of substances normally occur in the direction of concentration gradient/difference i.e. the difference in concentration of a substance across a membrane. Letting molecules diffuse or pass down their concentration gradient does not require energy but pumping those molecules against gradient requires energy in form of Adenosine triphosphate (ATP). This process is called Active transport.
In order to perform certain cellular processes, cells need to move substances from their surroundings into the cell across their cell membrane. Moving this substances against the concentration gradient between the cell membrane and its extracellular fluid requires energy (ATP).
An example is the sodium-pottasium pump employed by animal cells in which they expend energy to move K+ molecules into the cell and Na+ molecules outside the cell against the concentration gradient of their cell membrane and extracellular solution.
Red blood cells are disc shaped. It is thought one factor that allows them to have this shape is because they do not have a nucleus. This tends to increase amount of space inside the cell for hemoglobin.
They have a flexible disc shape which helps increase the surface- to- area volume ratio which enables oxygen and carbon dioxide to diffuse across the red blood cell's plasma membrane more readily.
Their disc shape also enables them to squeeze through tiny capillaries that are half their size .
You can use dimensional analysis to figure this out.
× 
= 3 grams
If done correctly, ml and ml will cancel out, leaving you with grams.
If you don't know dimensional analysis, simply multiply <em>3 ml</em> by <em>1 grams </em>and that should still get you 3 grams.
