Circles represent the most acidic hydrogens in these molecules. Which of the following is the correct representation?

Which of the following is an incorrect relation between the given pairs?

How many of the given compounds show tautomerism?

$A$ 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

Which of the following molecules is not chiral?

The method of preparing an optically active substance from a symmetric molecule in the presence of an optically active substance is called .....