Correct statements among the following  are
A) Glycine is optically inactive
B) Alanine can form Zwitter ion
C) Most of the naturally occuring amino acids belong to D–series
D) Cystine and methionine contain sulphur.

• A

  A, B, D only

• B

  A, B, C, D

• C

  A, C, D only

• D

  A, D only