Hello, I'm slightly confused with the following:
Debe de haber llovido esta noche, porque los coches están mojados.As you can see from the previous examples, when we use deber with this nuance of assumption/wondering, we can optionally use the preposition "de" after deber.
So you are saying that "de" is truly optional and has the same meaning whether "de" is used or not?
Thank you,
Dave
