Blue and green are usually not a good （相配）.
Neil Armstrong said that one small （一步） for a man，one giant leap for mankind.
Modern （医学）is developing fast.As a result，many diseases can be prevented or cured.
Look!The children are enjoying （他们自己） in the playground.How happy they are!
— Amy，can you lend me your （照相机）tomorrow？
— No problem.