1. The old man was too tired to walk on.
  The old man was _______ tired _______ he couldn't walk on.
2. Mike is the tallest in his class.
  Mike is taller _______  ________  ________  ________ in his class.
3. I will go to bed when I finish writing the letter.
  I _______ go to bed _______ I finish writing the letter.
4. It's about half an hour's walk.
  It takes about half an hour to go there _______  ________.
5. Work hard, and you will get good marks.
  _______  _______ work hard, you'll get good marks.
6. John was busy at 9 last night.
He was writing his English composition at 9 last night.
John _______  _______  ________ his English composition at 9 last night.