1. a. He spent the whole afternoon making a model ship.
    b. They spent a long time watching and recording the habits of animals and insects.
  2. a. They would collect all kinds of creatures.
    b. My grandfather would often go fishing before the sun rose.
  3. a. I had nothing but stories in my head at that time.
    b. We could see nothing but the sky and the sea around us.
  4. a. The bools became more and more popular.
    b. The days are getting shorter and shorter.
  5. a. They discovered they had much in common.
    b. The tow brothers seem to have little in common.
  6. a. She wanted to make sure that the district was preserved for future generations.
    b. Please make sure again (that) everybody has arrived.