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and 
are
A
Resonating structures
B
Tautomers
C
Geometrical isomers
D
Optical isomers
Detailed Solution
The two structures are of the enolate ion of acetone. In the first, the negative charge is on the carbon next to the C=O group. In the second, the electrons have moved to form a C=C bond and the negative charge is on oxygen.
Only the electrons (the $\pi$ electrons and the lone pair) are differently arranged; the positions of all the atoms, including hydrogen atoms, are exactly the same.
Structures that differ only in the arrangement of electrons are resonating structures (canonical forms) of the same species.
Tautomers differ in the position of an atom (usually H), e.g. keto and enol forms of acetone.
So these are resonating structures.
Only the electrons (the $\pi$ electrons and the lone pair) are differently arranged; the positions of all the atoms, including hydrogen atoms, are exactly the same.
Structures that differ only in the arrangement of electrons are resonating structures (canonical forms) of the same species.
Tautomers differ in the position of an atom (usually H), e.g. keto and enol forms of acetone.
So these are resonating structures.