Answer : The number of iron atoms present in each red blood cell are, 
Explanation :
First we have to calculate the moles of iron.

Now we have to calculate the number of iron atoms.
As, 1 mole of iron contains
number of iron atoms
So, 0.0519 mole of iron contains
number of iron atoms
Now we have to calculate the number of iron atoms are present in each red blood cell.
Number of iron atoms are present in each red blood cell = 
Number of iron atoms are present in each red blood cell = 
Number of iron atoms are present in each red blood cell = 
Therefore, the number of iron atoms present in each red blood cell are, 
The net ionic equation of the reaction could be determined by cancelling out the like ions between both sides of the reaction. These ions are called spectator ions. They are called as such because they do not actively participate in the reaction. The spectator ions are Na+ and Cl-. When you cancel those, the equation would become letter D.
Heat energy is absorbed by the substance.