How many representations of lactic acid are possible in Fischer projection (d & I) ?

There are 24(= 4!) this being the number of permutations of 4 ligands among 4 sites) ways of writing the projection formula ; 12 correspond to one enantiomer and 12 to the other. Twelve of these, corresponding to the (+) enantiomer, are depicted in Fig. ; the 12 mirror images of those shown would represent the (-) isomer.

 

Twelve representations of (+)-lactic acid (Fischer projections)