Answer: The correct option is A.
Explanation: In a chemical reaction, reactants react to form a number of products.
For the formation of products, the bonds of the individual reactants must be broken and the bonds of the products must be formed.
For example: Formation of water from hydrogen gas and oxygen gas. Reaction follows:

The Bonds of hydrogen and oxygen molecule are broken and new bonds between hydrogen and oxygen atoms are formed to give water molecule.
<u>Answer:</u> The products of the given chemical equation are 
<u>Explanation:</u>
Protonation equation is defined as the equation in which protons get added in the substance.
The chemical equation for the protonation of carbonate ion in the presence of water follows:

By Stoichiometry of the reaction:
1 mole of carbonate ion reacts with 1 mole of water to produce 1 mole of hydrogen carbonate ion and 1 mole of hydroxide ion
Hence, the products of the given chemical equation are 
Answer: A
Explanation: Protons and neutrons form the nucleus of the atom, with electrons orbiting it.
The standard atomic weight is the average mass of an element in atomic mass units ("amu"). Though individual atoms always have an integer number of atomic mass units, the atomic mass on the periodic table is stated as a decimal number because it is an average of the various isotopes of an element.