Final answer:
The D/L system for amino acids is based on the absolute configuration of glyceraldehyde. Most amino acids have the L configuration, except for a few exceptions. The chiral amino acids are mostly S configuration, except for cysteine which is R configuration.
Step-by-step explanation:
The D/L system for amino acids is based on the absolute configuration of glyceraldehyde. The D/L system assigns the L configuration to most amino acids, with a few exceptions. The assignment of absolute configuration is done using the Cahn-Ingold-Prelog priority rules, and it shows that most chiral amino acids are S except for cysteine, which is R.