一.语法填空（每空2分，共20分）
We often think of future. We often wonder 1. ________the world will be like in a hundred years' time.
Think of space. Perhaps a permanent station 2. ________ the moon will have been3. _________ (set up). Perhaps people will be able to visit the moon as 4_________(visit). Cheap rockets for space travel will have been developed, 5.________ (permit) long journeys through the solar system. When that time comes, people will be taking holidays in space and visiting 6. ________ planets. Great progress will have been made in medicine, too. Perhaps a cure will have been discovered for the most terrible of all diseases-cancer. Pollution is a problem we must solve. In a hundred years' time it will have been controlled.
