Choose the statement that best describes the given compounds.

Which of the following compounds has a plane of symmetry?
$R = -CH(Cl)-CH_3$
$S = -CH(Cl)-Br$

Which of the following molecules does not contain two chiral carbon atoms?

The relationship between the given pair $(A)$ and $(B)$ is:

$A$ pair of stereoisomers might be classified in various ways. Which of the following statements are true with respect to pairs of stereoisomers?
$a$. They might be configurational isomers
$b$. They might be diastereomers
$c$. They might be constitutional isomers
$d$. They might be tautomers
$e$. They might be conformational isomers
$f$. They might be enantiomers
$g$. They might be positional isomers

After prolonged treatment of $(A)$ by $D_2O/DO^-$, the difference in molecular weights of compounds $(A)$ and $(B)$ is: