Draw the Fischer projection of (2S,3R)-2,3-dihydroxybutanoic acid, and label it as erythro or threo.

Fischer Projection

A two-dimensional representation of a molecule's structure to display chirality by projecting asymmetric carbon atoms.

(2S,3R)-2,3-Dihydroxybutanoic Acid

A specific stereochemical form of dihydroxybutanoic acid, an organic compound with two hydroxyl groups located at the second and third carbons.

Erythro

A descriptor in stereochemistry denoting molecules with similar substituents on the same side in a Fisher projection.