When benzyl alcohol is oxidised with $KMnO_4$,the product obtained is

Ethanol cannot be dried by anhydrous $CaCl_2$ due to the formation of the following solvated product:

In the following reaction sequence,the compound $I$ is:
$I (C_3H_6Cl_2)$ $\xrightarrow{KOH_{(aq)}} II$ $\xrightarrow{(i) CH_3MgBr, (ii) H_2O/H^{+}} III$ $\xrightarrow{Anhy. ZnCl_2 + Conc. HCl}$ gives turbidity immediately.

When vapours of a secondary alcohol are passed over heated copper at $573 \; K$,the product formed is:

The order of reactivity of the following alcohols toward $HCl$ is:
$(1)$ $F-CH_2-CH_2-CH(OH)-CH_3$
$(2)$ $F-CH_2-CH_2-CH_2-CH(OH)-CH_3$
$(3)$ $CH_3-CH(OH)-CH_3$
$(4)$ $Ph-CH_2-CH_2-OH$

Which of the following reagents cannot be used to oxidize primary alcohols to aldehydes?