Identify A and B in the following reaction sequence.

The product (C) in the below mentioned reaction is :

$$\mathrm{CH}_3-\mathrm{CH}_2-\mathrm{CH}_2-\mathrm{Br} \xrightarrow[\Delta]{\mathrm{KOH}_{(\text {alc) }}} \mathrm{A} \xrightarrow{\mathrm{HBr}} \mathrm{B} \xrightarrow[\mathrm{KOH}_{(\mathrm{aq})}]{\Delta} \mathrm{C}$$

Given below are two statements:

Statement - I: High concentration of strong nucleophilic reagent with secondary alkyl halides which do not have bulky substituents will follow $$\mathrm{S}_{\mathrm{N}}{ }^2$$ mechanism.

Statement - II: A secondary alkyl halide when treated with a large excess of ethanol follows $$\mathrm{S}_{\mathrm{N}}{ }^1$$ mechanism.

In the light of the above statements, choose the most appropriate from the options given below:

Example of vinylic halide is :