Which of the following on oxidation forms $propanone$?

Product $A$ is$:-$
$H-CHO \xrightarrow[(ii) D_2O]{(i) C_6H_{11}MgBr} A$

An optically active alcohol of formula $C_9H_{12}O_2$ produced the following compound when refluxed with $KMnO_4$. What is the structure of $(A)$? The original compound showed these properties also:
$\mathop {C_9H_{12}O_2}\limits_{(A)} \xrightarrow{Na} H_2 \text{ liberated}$
$\mathop {C_9H_{12}O_2}\limits_{(A)} \xrightarrow{Br_2} \text{ no rapid reaction}$
$\mathop {C_9H_{12}O_2}\limits_{(A)} \xrightarrow[{cool}]{CrO_3 / H^{+}} C_9H_8O_3$

Identify the product $P$ of the following reaction:
$CH_3OH + CH_3MgX \longrightarrow P + MgX(OCH_3)$

The best method to prepare cyclohexene from cyclohexanol is by using

Which of the following alcohols is least soluble in water?