How many asymmetric centers are present in the open chain form of the aldohexose ?

             FOUR asymmetric centers are present in the open chain form of the Aldohexose d-(-)-Gulose.

Explanation:
                   Here the word Asymmetric center means those carbon atoms which contains atoms or group of atoms different from each other. All the four atoms or group of atoms attached to carbon atom are different and have different molecular masses. Such carbon atoms are also called as Chiral carbons. The structure of d-(-)-Gulose is drawn below, and all Four Asymmetric centers are pointed by " * "