My hometown had a shop where the owner made three kinds of donuts every morning: plain donuts, powdered sugar donuts, and cinnamon donuts. He also had a sign above each tray of donuts; the signs read THEM, THESE, and THOSE.
During the day, customers would make requests, such as, "I'd like two cinnamon donuts, and a plain donut," and whoever was behind the counter would put those in a bag. But if the shop owner happened to be behind the corner – mind you, this man was known for being a little eccentric – he would look at you as if he didn't understand, and say something like, "Look, we have Them, These, and Those – now what can I get for ya?" whereby the customer would have to say, "I'll take one of Them, and two of Those."
I always marveled at the way, no matter what combination of donuts you were ordering, you could still create a grammatically correct sentence using his names for the donuts, such as, "I'd like three of them, one of these, and two of those."
My point for relating this story is that sometimes these words (those words?) can be used interchangeably, with little or no change in meaning.
I'd say that, in the general case, these seems to imply closer proximity then those (as in, "These marbles [in my hand] look very pretty, but those marbles [behind the counter] don't look as nice.") However, as the donut example illustrates, even this generality doesn't always hold true.
Back to your example: I think you could have used either these or those, and, much like at the donut counter, either word would work just fine.
I think the sentence #1 and 4 are grammatically wrong as "until yesterday"doesn't fit in the present perfect or in the present simple.
As for the sentences "2 and 3, they are grammatically correct as they refer to things that happened in the past, for which we can use "until yesterday".
Best Answer
Normally, you would say this:
"Final exams" doesn't need an article here since you're talking about final exams in general. You would only say "the final exams" if you wanted to talk about a specific group of exams.
This means that someone or something caused the final exams to start. This is unusual. In English, final exams are an event, not a process or machine.
A native speaker would probably understand this, but it's bad grammar. You could say "Final exams are starting", but that doesn't mean the same thing.