Ответ:

Краткое пояснение: В упражнении нужно составить предложения, используя Present Perfect Continuous.
  1. Have a rest now. You have been working too hard lately.
  2. You are shivering. Have you been standing in this cold long?
  3. Her hands are red and wet. She has been scrubbing the floors for three hours.
  4. The children are quite voiceless. They have been singing at the top of their voices since morning.