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Chlorination of $$n-butane$$   takes place by free radical mechanism as follows :

$$ - CN$$  has highest priority. Further the sum of locants is 7 in (b) and 9 in (d).

Highly electronegative atom makes the bond more polar.

IUPAC name - 3, 3 - Dimethyl -1 cyclohexanol

Higher stability of allyl and aryl substituted methyl carbocation is due to dispersal of positive charge due to resonance

whereas in alkyl carbocations dispersal of positive charge on different hydrogen atoms is due to hyper conjugation hence the correct order of stability will be

 It has complete octet for all atoms.

$$\eqalign{ & {\text{Mass of}}\,\,{H_2}O = 0.54\,g \cr & {\text{Mass of}}\,\,C{O_2} = 0.88\,g \cr & \% \,{\text{of}}\,\,C = \frac{{12}}{{44}} \times \frac{{0.88}}{{0.46}} \times 100 \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 52.17\% \cr & \% \,{\text{of}}\,\,H = \frac{2}{{18}} \times \frac{{0.54}}{{0.46}} \times 100 \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 13.04\% \cr & \% \,{\text{of}}\,\,O = 100 - \left( {52.17 + 13.04} \right) \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 34.79\% \cr} $$

when $$X$$ is $$Cl$$  the $$C - X$$  bond is more polar and ionic which leaves the compound more reactive for nucleophilic substitution reaction.