The correct acidity order of phenol (I), 4-hydroxybenzaldehyde (II) and 3-hydroxybenzaldehyde (III) is

The correct order of C = O bond length in ethyl propanoate (I), ethyl propenoate (II) and ethenyl propanoate (III) is

Select the molecule in which all the atoms may lie on a single plane is

The correct stability order of the following carbocations is

(I) $$\mathrm{{H_2}\mathop C\limits^ \oplus - CH = CH - C{H_3}}$$

(II) $$\mathrm{\mathop C\limits^ \oplus {H_2} - CH = CH - BM{e_2}}$$

(III) $$\mathrm{{H_2}\mathop C\limits^ \oplus - CH = CH - NMe}$$

(IV) $$\mathrm{{H_2}\mathop C\limits^ \oplus - CH = CH - OMe}$$