I believe the answer is choice 2. And if you don’t mind, please look at my recent mathematics post and help me.
EST stands for eastern. If a show is coming on at 8 Pm EST, it is coming on at 8 PM on the east coast.
The sentence that is punctuated correctly is, option A. We grated one-third of that hunk of cheddar cheese. We use a hyphen for the word "one-third" because it is a compound word. A compound word consists of two or more words joined together to form a new word and meaning.