if I'm not mistaking it would be the second option
The answer is b
the slow down because of the change of form into solid and they pack together to form the solid
The most abundant greenhouse gas is water vapor.
Chromosomes abnormalities often happen due to one or more of these:
Errors during of sex cells (meiosis)
Errors during of other cells(mitosis)
Substances that causes birth defects (teratogens)
Answer : The oxygen will appears in the final chemical equation as a reactant.
Explanation :
The given chemical reactions are:
(1) 
(2) 
Now we are adding reaction 1 and reaction 2, we get the final chemical equation.
The final chemical equation is:

Thus, the oxygen will appears in the final chemical equation as a reactant.