Indicate which of the following statements is true: a) Leucine and valine are position isomers and, because they have an asymmetric carbon, both ha...

Indicate which of the following statements is true:
a) Leucine and valine are position isomers and, because they have an asymmetric carbon, both have a pair of enantiomers.
b) Leucine and isoleucine are position isomers and, because they have an asymmetric carbon, both are optically active.
c) Leucine and isoleucine are position isomers and, because they have an asymmetric carbon, both have a pair of enantiomers.
d) Leucine and isoleucine are functional isomers and are not optically active.
e) Valine and isoleucine are chain isomers, but only valine is optically active.

a) I and II are correct.
b) II and IV are correct.
c) III and V are correct.
d) IV and V are correct.
e) I and III are correct.