Major product $A$ is

The final product $A$,formed in the following reaction sequence is:
$Ph-CH=CH_2$ $\xrightarrow[\text{(iii) } HBr, \text{ (iv) } Mg, \text{ ether, then } HCHO / H_3O^{+}]{\text{(i) } BH_3, \text{ (ii) } H_2O_2, OH^{-}} A$

$HBr$ reacts fastest with

Identify the organic product formed when ethylene glycol is heated with acidic potassium permanganate $(KMnO_4)$.

The product $(B)$ of the reaction sequence is:
$Cl-C_6H_4-CH_2Br$ $\xrightarrow{Mg, Et_2O} A$ $\xrightarrow[2. H_3O^+]{1. CH_3CHO} B$

Which of the following would undergo dehydration most readily?