D.

No one knows. When glass blowing techniques modernized in the 19^th century, one of the more curious assumptions was the idea that white wine glasses should be smaller than red. Was white wine considered lesser in potential complexity and importance? Less in need of oxygen to open up? Neither is true. Some scholars surmise that white wines were associated with femininity and therefore served in smaller glasses. (Sigh). Or maybe there was a simple, practical reason. Before the advent of refrigeration, white wines would have been served only cellar-cool. Maybe smaller glasses were intended for smaller pours and more frequent topping up, to keep the white wine as cool as possible. Today, of course, there’s no need for separate white wine and red wine glasses.