The correct answer is 2.
In oxidation-reduction reactions (or redox reactions), a number of electrons are transferred between two species. During this process, the oxidation number of an atom (or molecule or ion) changes by receiving or losing an electron.
Answer to this is O-atom.
Explanation: The Bronsted acid-base theory is the backbone of chemistry. This theory focuses mainly on acids and bases acting as proton donors or proton acceptors.
where 
is the Lewis Acid and 
is the Lewis Base and 
is the Covalent Bond.
Reaction of dissociation of 
in 
is given as:
In this reaction O-atom has lone pair in water and therefore it accepts the proton from 
forming a Lewis Base.
To communicate the results in an organized report
The (B) answer (B) is (B) (B) (B)
Although 1013.25 mb (760 mm Hg) is considered to be the standard atmospheric pressure at sea level, it does not mean that the pressure at this level has this value, actually this being 1011 mb.
