Identify $Z$ in the following reaction sequence:
${C_2}{H_5}I$ $\xrightarrow{Alc. KOH} X$ $\xrightarrow{Br_2} Y$ $\xrightarrow{KCN} Z$

Write in detail about the hydrogenation of unsaturated hydrocarbons.

Identify product $A$ and product $B$ for the following reaction:

The major product of the following reaction is:

When $2-$Methylbut$-2-$ene is treated with hydrogen chloride,the major product formed is

Assertion $(A)$: Reaction of but$-1-$ene with $HBr$ gives $1-$bromobutane as major product.
Reason $(R)$: Addition of hydrogen halides to alkenes proceeds according to Markownikoff's rule.
The correct answer is