Amongst the following,the major product of the given chemical reaction is $.....$ .

In the following reaction,$A$ and $B$ respectively are
$A \xrightarrow{HBr} C_2H_5Br \xrightarrow{B} A$

Reaction of but$-2-$ene with acidic $KMnO_4$ gives:

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A)$: Cis form of alkene is found to be more polar than the trans form.
Reason $(R)$: Dipole moment of trans isomer of $2$-butene is zero.
In the light of the above statements,choose the correct answer from the options given below:

Which products are obtained on reaction of but$-1-$ene with $HBr$ in the presence of peroxide?

How many of the following compounds on reductive ozonolysis produce formaldehyde $(HCHO)$ as one of the products? The compounds are: $1$-butene,$2$-butene,$2$-methyl-$1$-butene,cyclopentene,cyclobutene,$1$-methylcyclopropene,methylenecyclopropane,$1$-methylcyclopropene (isomer),and cyclohexene.