$A$ on heating isomerizes to $B$. What is the structure of $B$?

Ethyl alcohol will give ethyl chloride with the help of which of the following?

In the reaction sequence $CH_2=CH_2$ $\xrightarrow{HOCl} X$ $\xrightarrow{Y} CH_2(OH)-CH_2(OH)$,$X$ and $Y$ respectively are:

$A$ compound with formula $C_4H_{10}O$ on oxidation gives $C_4H_8O$,which forms an oxime and gives a positive iodoform test. The original compound on reaction with concentrated $H_2SO_4$ gives $C_4H_8$. What is the structure of the compound?

Which of the following statements is correct regarding the rate of dehydration in alcohols?

Which of the following is a secondary benzylic alcohol?