Sure, here are the correct forms of the words given in brackets:

1. The university has **authorized** the use of dictionaries during language examinations. (author)
2. It is very difficult to find Mrs. Burton's shop, for it was **distinguished** from all others in the street. (distinguish)
3. He is very generous. Everyone admires his **unselfishness**. (selfish)
4. **Leadership** skill is the one skill that can grant you the opportunity to get a good job. (lead)
5. **Conservationists** are alarmed by the rate at which tropical rainforests are being destroyed. (Conserve)
6. I believe in **preventing** diseases because **prevention** is always better than cure. (PREVENT)
7. The coal industry was **originally** private but was **nationalized** in the 1940s. (ORIGIN/NATION)