Explanation

(b)
In $C_{2}H_{5}$ each C-atom is sp-hybridised which contains 50% $s$-character. The greater the $s$-character of an orbital, the bonding electron pair will be more inclinated towards the nucleus as a result carbon would acquire a negative charge and hydrogen a positive charge. Hence, it is acidic in nature.
$H - C \equiv C:H$
$sp$ $sp$
and removal of hydrogen as proton takes place.