III only

Both I and III

Both I and II

Both II and III

the eclipsed conformation of ethane is more stable than staggered conformation even through the eclipsed conformation has torsional strain

the staggered conformation of ethane is more stable than eclipsed conformation, because staggered conformation has no torsional strain

the staggered conformation of ethane is less stable than eclipsed conformation, because staggered conformation has torsional strain

the eclipsed conformation of ethane is more stable than stggered conformation, because eclipsed conformation has no torsional strain.

atropisomers

enantiomers

mesomers

diastereomers

Ammonia is a nucleophile.

Nucleophiles attack low e^$$-$$ density sites.

Nucleophiles are not electron seeking.

Nucleophile is a Lewis acid.