用动词的适当形式填空:
1. ____________（support）his family, he
  had to work hard in a chemical works.
2. I noticed him ______（slide） into the
  room through the back door.
3. Scientists are working on a new vaccine
  （疫苗）____（rid）the country of the
  terrible disease.
4. Respecting others is _____(repect) by
  others.
5. The museum had several painting
  ______(represent) the artist’s early style.
6. Everything worth _____(regret) is gone and
  there is nothing ____(regret) now.
7. The book _____(refer to) ...