Why don't you wear summer clothes?

Why didn't you tell it to me in advance?

Why were you silent all the time?

Why did her father go to Japan?

Hey, Molly, why don't you come?

Why don't you stay a little while?

Why don't you give it another try?

Why don't you ask Mr White?

Why did Bill tear the letter into pieces?

The pilot explained to us why the landing was delayed.