Which one of the following is an electrophilic addition reaction?

What will be the major product of the following sequence of reactions?
$n-Bu-C \equiv CH \xrightarrow[(ii) \text{Lindlar cat.}, H_2]{(i) n-BuLi, n-C_5H_{11}Cl}$

$A$ compound $X$ absorbs $2$ moles of hydrogen and $X$ upon oxidation with $KMnO_4 \mid H^{+}$ gives the products shown below:
$CH_3-CO-CH_3$,$CH_3-COOH$ and $CH_3-CO-CH_2-CH_2-COOH$.
The total number of $\sigma$ bonds present in the compound $X$ is . . . . . .

Which of the following alkenes will give $CH_3CH_2CHO$ and $CH_3COCH_3$ upon ozonolysis?

$CH_2=CH_2 \xrightarrow{Br_2/H_2O} A$. In the above reaction,the compound $A$ is:

$1-$Phenylbut$-1-$ene on ozonolysis gives