Answer:
Explanation: A chemical change is a reaction in which chemical composition of the substance changes. Some bonds are broken and some new bonds are formed.
The reactants are written in terms of their chemical formula on the left hand side and the products are written in terms of their chemical formula on right hand side with a arrow in between. The chemical symbols are followed by their physical states such as (l) for liquid, (s) for solid, (g) for gas and (aq) for aqueous.
Thus the only reaction producing a gas is 
Answer:
The answer to your question is probably false
B. normal contact force acts in the opposite direction as of weight, hence A is out. C is out as if normal contact force is lesser than the weight, the object would be sinking into the ground due to net force of the weight. D is out as if normal contact force is greater than the weight, the object would be flying upwards.