0 used with another verb to form questions and negative sentences, including negative orders, and sometimes in affirmative sentences for reasons of style: --
Where do you work?
Why did you do that?
"Didn't you realize she was deaf?" "No I didn't."/"Of course I did."
Don't (you) speak to me like that!
formal So quietly did she speak (= she spoke so quietly) that I could scarcely hear her.
Little does he know (= he knows nothing about it), but we're flying to Geneva next weekend to celebrate his birthday.
"I want two chocolate bars and an ice cream." "Do you now/indeed? (= that is surprising or unreasonable)."
You don't understand the question, do you?
3 to perform, take part in, or achieve something: --
That was a really stupid thing to do.
What are you doing over the weekend?
UK Why were you sent to see the headmaster? What have you done now?
US Why were you sent to the principal's office? What did you do now?
UK What have you done (= made happen) to her?
US What did you do (= make happen) to her?
What (on earth) were you doing in the library (= why were you there) at two o'clock in the morning?
What are these toys doing here? (= Why are they here?)
What can I do for you? (= How can I help you?)
UK What have you done with (= where have you put) my coat?
US What did you do with (= where did you put) my coat?
She just hasn't known what to do with herself (= how to keep herself busy) since she retired.
It's a global problem - what can individuals do about it?
We can complete it step by step however long the road is and it can't be completed however short the road is if you don't even mark your footprint.
Можем да го завършим стъпка по стъпка, колкото и дълъг да е пътят и не може да бъде завършен, колкото и кратък да е пътят, ако дори не маркирате отпечатъка си.