Maltotriose is found in malted grains and is a product of the breakdown of starch. Based on its Haworth structure, what monosaccharide units are present in maltotriose?

two units of α-D-glucopyranose and one unit of β-L-glucopyranose

three units of α-D-glucopyranose

three units of β-D-galactopyranose

two units of β-D-galactopyranose and one unit of α-L-galactopyranose