Which of the following is the most suitable reagent for the conversion of $RCH_2OH$ to $RCHO$?

Which of the following alcohols requires acidic $KMnO_4$ to convert it into an aldehyde or ketone?

Arrange the following compounds in decreasing order of their boiling point $(BP)$:
$CH_3CHO$ $(I)$,$CH_3CH_2OH$ $(II)$
$CH_3OCH_3$ $(III)$,$CH_3CH_2CH_3$ $(IV)$

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

What is obtained by the reaction of primary and secondary alcohols with red-hot copper at $573 \ K$?

$HO-CH_2-CH_2-OH$ on heating with periodic acid gives: