请告诉我中国古代的四大发明是什么，并用json格式按照"invention":"发明名称","significance":"重要性"的格式输出，每项发明单独一行。
user
```json
{
    "invention": "造纸术",
    "significance": "促进了书写和文化的传播"
}
{
    "invention": "指南针",
    "significance": "推动了航海和地理探索的发展"
}
{
    "invention": "火药",
    "significance": "改变了战争方式和武器技术"
}
{
    "invention": "活字印刷术",
    "significance": "加速了知识的传播和教育的普及"
}
```
assistant