Answer:
Farthest from the carbonyl carbon.
Explanation:
Reference carbon that determined the absolute D and L configuration is located farthest from the carbonyl carbon.
In other words, reference carbon is that assymentric carbon which is located farthest from the carbolyl carbon and has configuration similar to D- or L-glyceraldehyde isomers.
D and L configuration is decided by the direction of -OH group attached to the reference carbon.
In L-isomer, -OH group is attached to the left side of the reference carbon and in D-isomer, -OH group is attached to the right side of the reference carbon.
