Student or Learner
When turning a statement such as I gave my mother the keys or The guide was showing the tourists the city into a question about the indirect object, should the preposition to be mentioned at the end or can it be left out?
Who did you give the keys [to]?
Who was the guide showing the city [to]?
What about this one My mother bought me a present.
Who did your mother buy a present [for]?