Explanation

(d)
When ethyl alcohol is heated with conc. $H_{2}SO_{4}$ at $160{^\circ} - 170℃$ , the product obtained is ethylene ($C_{2}H_{4}$).
$CH_{3} - CH_{2}OH + H_{2}SO_{4} \rightarrow CH_{3}CH_{2}HSO_{4} + H_{2}O$
ethyl hydrogen sulphate
${CH}_{3}\ –{CH}_{2}{HSO}_{4}\underset{\mathrm{\Delta}}{\overset{160 - 170℃}{\rightarrow}}CH_{2} = CH_{2} + H_{2}SO_{4}$
ethylene
But at lower temperature ether is formed.