$3$ moles of ethanol react with $1$ mole of phosphorus tribromide to form $3$ moles of bromoethane and $1$ mole of $X$. Which of the following is $X$?

What will be $A$,$B$,$C$,and $D$ in the following reaction sequence?
Cyclohexanol $\xrightarrow[H_2SO_4]{CrO_3} A$ $\xrightarrow[(ii) H_3O^+]{(i) CH_3MgI} B$ $\xrightarrow{\Delta, H_2SO_4} C$ $\xrightarrow[(ii) H_2O_2, NaOH]{(i) (BH_3)_2} D$

The alcohol that produces turbidity immediately with $ZnCl_2 +$ conc. $HCl$ at room temperature is:

When wine is exposed to air,it becomes sour. The reason for this is -

Primary and secondary alcohols on action of reduced copper give

Which of the following alcohols reacts fastest with Lucas reagent and turns the solution turbid instantly?