Among the following, the reaction that proceeds through an electrophilic substitution, is :

Hydrocarbon (A) reacts with bromine by substitution to form an alkyl bromide which by Wurtz reaction is converted to gaseous hydrocarbon containing less than four carbon atoms. (A) is

With respect to the conformers of ethane, which of the following statements is true?

Predict the correct intermediate and product in the following reaction :

$${H_3}C - C \equiv CH\mathrel{\mathop{\kern0pt\longrightarrow} \limits_{HgS{O_4}}^{{H_2}O,{H_2}S{O_4}}} \mathop {Intermediate}\limits_{(A)} \to \mathop {\Pr oduct}\limits_{(B)} $$