1. The official group works to promote the status of elderly people as active and useful members of the community.
2. When we drove up to the four corners the police officer held up his hand as a signal for us to stop. (主要是four corners如果理解?)
3. These operations are a great success of modern medicine, with a success rate of more than 90 percent.(主要是operations如果理解?)
4. After winning the next term of office, the new government started to take steps to develop the national wealth.