Which of the following exhibits tautomerism?

Which of the following isomeric hydrocarbons is most acidic?

If a carbon atom is attached to $-H, -OH, -COOH$ and $-OCO^{-}C_2H_5$ groups,the number of chiral $C$ atoms in the molecule is:

Which of the following compounds are meso forms?

Find out the statements which are not true.
$A$. Resonating structure with more number of covalent bonds and lesser charge separation are more stable.
$B$. In electromeric effect,an unsaturated system shows $+E$ effect with nucleophile and $-E$ effect with electrophile.
$C$. Inductive effect is responsible for high melting point,boiling point and dipole moment of polar compounds.
$D$. The greater the number of alkyl groups attached to the doubly bonded carbon atoms,higher is the heat of hydrogenation.
$E$. Stability of carbanion increases with the increase in $s$-character of the carbon carrying the negative charge.
Choose the correct answer from the options given below.

Which of the following options is the correct order of relative stabilities of cations $I$,$II$,and $III$ as shown below (most stable first)?
$(I) \, C_6H_5CH_2^+$
$(II) \, CH_2=CH-CH_2-CH^+-CH_3$
$(III) \, (CH_3)_3C^+$