Can't remember this...
The subject of a sentence may be what parts of speech? Is it the preposition?
The subject always pairs with a verb, and verbs denote states or actions, so the subject must be something that can be described as a being in a state, or something doing an action, or undergoing an action. Prepositions, e.g., to, for, from, under, around, down, cannot function as subjects.
Hope that helps.