One difference between D-glucose and L-glucose is ________.
◦ it is not possible to make L-glucose
◦ L-glucose cannot form a closed structure
◦ only D-glucose can act as a substrate in metabolic reactions
◦ the open-chain form of L-glucose does not exist
◦ L-glucose has a 5-membered ring, and D-glucose has a 6-membered ring