Identify the (R) or (S) configuration of the asymmetric carbon atoms in the following molecules.

• A. (a) has R,S configuration
  (b) has S configuration
• B. (a) has S,S configuration
  (b) has R configuration
• C. (a) has R,R configuration
  (b) has no asymmetric carbon.
• D. (a) has R,S configuration
  (b) has no asymmetric carbon.

Answer: (D)