A declarative sentence is a statement. Such as, "I went to the park yesterday." That is declarative, because it is stating a fact. Another way to know it's declarative is, all declarative sentences end in periods. But you shouldn't get these mixed up with imperative which are commands. Hope this helped!
Birthday is the subject of the sentence. This is because t<span>he subject of a sentence is the person, place, thing, or idea that is doing or being something.</span>
