Ultrasound can pass even through solids why?

1. according to the article, the chinese government has tried to control its people in all of the following ways except: question 1 options: create and spread propaganda in the media censorship of the media allowing people to create their own social media deleting people's social media posts without their permission when a government has total control over its citizens, including the media, it is a of government question 2 options: constitutional monarchy parliamentary democracy autocracy presidential democracy 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 china wants to take control over social media in which other region? question 4 options: taiwan chile japan hong kong