Phosgene is formed slowly from which one of the following on exposure to air and sunlight?

The best method for the preparation of $Me_{3}CCN$ is

Which reagents shown below would accomplish the following transformation?
$Isopropyl \ bromide \xrightarrow{1. A \ 2. B} Isopropyl \ alcohol$

In $S_{N}2$ reaction,the carbon in the transition state is

The $S_N2$ product of the following reaction is:

Under the specified conditions,substrate $X$ undergoes substitution and elimination reactions to give products $A - D$. $A$ and $B$ are stereoisomers,but not enantiomers. $C$ and $D$ are enantiomers. $A$ is not an isomer of $C$. Which of the following could be the starting material $X$ ?
$X \xrightarrow[\Delta]{H_2O} A + B + C + D$