March 4 = March forth
Valentine's Day is the subject of that sentence.
Mrs. Marcus is the complete subject of the sentence.
No. There is no verb.
Yes, it is.
Valentine's Day is the subject of that sentence.
Yes, that's a complete sentence. Maybe somebody you really want to hear from will call tomorrow.
The superlative form is used: This is the hottest day of the year.
It is only capitalized if it is part of a name (Eg, Larry's Day Care) or at the start of the sentence; in this case you only capitalize 'day' and not 'care'.
Today is the coldest day of the year.
This is a fragment. To make it a sentence you could write " When Lola prepares for a day at the beach, she packs a big lunch."
It, because is is a verb
An offense which mandates a prison sentence of at least one year and one day is, by definition, a felony.