Maximum bond angle is present in

In the following sequence of reactions
$CH_3CH_2OH$ $\xrightarrow{P + I_2} A$ $\xrightarrow{Mg, \text{Ether}} B$ $\xrightarrow{HCHO} C$ $\xrightarrow{H_2O} D$
then compound $D$ is -

Ethanol when reacted with $PCl_5$ gives $A$,$POCl_3$ and $HCl$. $A$ reacts with silver nitrite to form $B$ (major product) and $AgCl$. $A$ and $B$ respectively are

In the following structure,the double bonds are marked as $I, II, III$ and $IV$. Geometrical isomerism is not possible at site$(s)$:

$A$ particle is moved from $(0, 0)$ to $(a, a)$ under a force $\vec F = (3\hat i + 4\hat j)$ along two paths. Path $1$ is $OP$ and path $2$ is $OQP$. Let $W_1$ and $W_2$ be the work done by this force in these two paths respectively. Then

Which of the following is the preferred site for injecting medication to ensure rapid action and minimize side effects?