infinitive after who, what, how etc

  • In reported speech, we can use an infinitive after the question-words who, what, where etc (but not why) to talk about questions and the answers to questions.
      [ verb + question-word + infinitive ]
      I wonder who to invite.
      Show me what to do.
      Can you tell me how to get to the station?
      I don’t know where to put the car.
      Tell me when to pay
      I can “t decide whether to answer her letter.
  • We cannot begin a direct question with How to…?what to…?etc.
    We often use shall or should.
      How shall I tell her?
      What shall we do?
      Who should I pay?