The conversion shown below can be brought about by?

At low temperatures,the slow addition of molecular bromine to $CH_2=CH-CH_2-C \equiv CH$ gives :-

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

The reaction of ethylene with bromine in a methanol solution yields $1, 2-$dibromoethane as well as $BrCH_2CH_2OCH_3$. This is because ......

Number of shared electrons between carbon-carbon atoms in an ethylene molecule is

Which of the following is the product of the reductive ozonolysis of $1-$methylcyclohexene?