A、It came from a river. B、It was extremely pure. C、It was found in large quantities. D、It was dug up from a deep mine. A

Scientists in China recently discovered the remains of a very old village where salt was produced 4,000 years ago. At the site, called Zhongba which is located at the Gan River in the Chongqing Municipality, the scientists found small cups still containing traces of ancient salt. Based on this discovery, they believe that 4,000 years ago people of the village used the cups to boil salty water. Once the water became steam, the salt was left behind.
    The Zhongba settlement is extremely important because it is the first place we know of where people had a method for collecting salt. Comparable evidence of ancient salt production in the world comes from sites that not nearly as old. The Zhongba settlement is also very different from other sites because of its unique source of salt. While in other places salt was dug from mines or obtained from sea water, the Zhongba salt was obtained from a salty river. Regardless of the source, the Zhongba people must have valued salt greatly because salty foods were not as common then as today. Such foods would have been difficult to find, and they were probably a rare luxury. But even though salt was scarce, people knew about it,and it was appreciated in the past just as much as it is today. What the discovery at Zhongba shows is that people have had a taste for salt for four thousands of years!
Questions 11 to 12 are based on the passage you have just heard.
11. Where did the scientists find traces of salt?
12. What was unusual about the salt at Zhongba?