Yes your choices of B C D are right 
        
             
        
        
        
Answer:
The oxidation number of the metal decreases
2 Al  + Fe₂O₃ → Al₂O₃ + 2 FeO
The metal element iron, is reduced from Fe⁺³ in Fe₂O₃ to Fe⁺² in FeO
Explanation:
When an element gains electron, the element becomes reduced, hence when a metal is reduced, the metal gains electrons, which reduces the oxidation number of the metal 
An example of a metal being reduced is;
2 Al  + Fe₂O₃ → Al₂O₃ + 2 FeO
In the above reaction, the iron (III) oxide is reduced to iron (II) oxide by aluminium metal.
 
        
             
        
        
        
441 g CaCO₃ would have to be decomposed to produce 247 g of CaO
<h3>Further explanation</h3>
Reaction
Decomposition of CaCO₃ 
CaCO₃ ⇒ CaO + CO₂
mass CaO = 247 g
mol of CaO(MW=56 g/mol) :

From equation, mol ratio CaCO₃ : CaO = 1 : 1, so mol CaO :

mass CaCO₃(MW=100 g/mol) :

 
        
             
        
        
        
The formula is easy:
Gram formula mass
----------------------------
Emprical Formula
So if we plug in our own numbers,
114.0
--------
57.116 
We get an answer of 1.99, which rounds to 2.
Then, we distribute based off of our empirical formula.
2(C4H9) becomes C8H18.
Our molecular formula is C8H18.
Hope I could help!
        
             
        
        
        
2H2O --> 2H2 + O2
The mole H2O:mole O2 ratio is 2:1
Now determine how many moles of O2 are in 50g: 50g × 1mol/32g = 1.56 moles O2
Since 1 mole of O2 was produced for every 2 moles of H2O, we need 2×O2moles = H2O moles
2×1.56 = 3.13 moles H2O
Finally, convert moles to grams for H2O:
3.13moles × 18g/mol = 56.28 g H2O 
D) 56.28