Which of the following biphenyls is optically active?

$R$ and $S$ configuration of compound $(A)$ & $(B)$ will be

Which of the following reaction$(s)$ give$(s)$ a meso-compound as the main product?

$A$ 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

The number of chiral centres present in $[B]$ is

What is the relationship between the following molecules?