Ethyne $\left(\mathrm{C}_2 \mathrm{H}_2ight)$
Number of $\sigma$-bonds at $\mathrm{C}$-atom $=2$
Number of lone pair of electrons at $\mathrm{C}$-atom $=0$
$\therefore$ Total $=2+0=2$
$\therefore$ Hybridisation is $\mathrm{sp}$.
$\therefore \mathrm{C}_2 \mathrm{H}_2$ is linear
Methane $\left(\mathrm{CH}_4ight)$
Number of $\sigma$ bonds at $\mathrm{C}$-atom $=4$
Number of-lone pair of electrons at C-atom $=0$
$\therefore$ Total $=4+0=4$
$\therefore$ Hybridisation is $\mathrm{sp}^3$.
$\therefore \mathrm{CH}_4$ is tetrahedral.
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