根据括号中的要求改写下列句子。 1. He is going to Shanghai. (用现在完成时) ______________________________________ 2. I heard about the news about the space travel. (改为同义句) ______________________________________ 3. Scientists have found life on other planets.(改为否定句) ______________________________________ 4. They haven't been to Mars. (用yet) ______________________________________ 5. The spacecraft has reached the moon. (用just) ______________________________________ 6. Many astronauts have visited the space station. (用already) ______________________________________ |