Discovered in the 800s and originally for fireworks what is one of the most important inventions of the tang and song dynasties

According to the article,"social credit" is question 3 options: an experiment to people talk on-line a farming experiment that hurt people under mao ze dong using someone else's data from the internet, to give or take away things such as the right to buy an airline ticket a credit you get in china for having friends in real life, and not just on social media