Total number of isomeric compounds (including stereoisomers) formed by monochlorination of $2-$methylbutane is................ 

Total number of stereoisomers possible for following compound is

Amongst the following amino acids, the $(R)$ - enantiomer is represented by

A pair of stereoisomers might be classified in various ways. Which of the  following statement 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 having plane of symmetry ?

The molecules represented by the above two structures are