How does the variability of the head group in sphingolipids lead to different classes?

Only phosphodiester linkages lead to different classes of sphingolipids.

Different chemical groups can attach via phosphodiester or glycosidic linkages, creating distinct classes of sphingolipids.

Only glycosidic linkages lead to different classes of sphingolipids.

The head group variability does not affect the classification of sphingolipids.