Michael Swan explains this clearly in his Practical English Usage (2005.481).
When who, which, what or whose is the subject (or part of the
subject), do is not normally used: Compare:
- Who phoned? (Who is the subject.)
- Who did you phone? (Who is the object.)
[...] But do can be used after a subject question word for emphasis,
to insist on an answer:
- Well, tell us - what did happen when your father found you?
This is not a normal English grammar structure.
The rules of Jeopardy require that contestants answer the clue in the form of a question.
I tend to think of it this way... it's a backwards game show. Most game shows require that the host ask a question:
Who was the first president of the United States of America?
And contestants provide the answer:
George Washington.
With Jeopardy, it's the other way around. The host is answering the question while the contestants are asking it...
So, if the clue is:
This man was the first president of the United States of America.
The rules require the response be
Who is George Washington?
If they fail to do this, even if they're technically correct, they lose points.
So, if a contestant answered:
George Washington.
They would be wrong by the rules of the game.
As to their hesitant tone, sometimes they're not completely sure of the answer, so they're guessing.
Best Answer
The difference between these two sentences is that the first one sounds like a question and the second one sounds like a guess or an uncertain statement. If you say:
you're saying that you don't know whether she won. If you say:
You're saying that you think she won, but you're not sure. You could also say this after someone else said she won, and you're confused or skeptical. For instance:
Here, Person 1 is surprise because he/she doesn't expect someone to cry when something good happens. His question expresses confusion and mild disbelief.
When talking about someone else's actions, "that" is more common than "it". Also, in casual speech, the "that" in "mean that she" may be dropped. So a more natural, casual version of the first sentence is: