I believe the answer is: <span>syntax
</span>In English language, <span>syntax refers to the words arrangement that make a sentence considered 'well-formed' and could be understood.
For most children, the development of </span><span>syntax could only appear when they're 5 years old or older.</span>
4. Harsh climate conditions
Chinese government pushed for improving water resource management and pollution control in the Hai Basin. The Hai Basin had serious water-related issues like pollution, shortage, etc. With the help of the World Bank and the Chinese government, they fixed Bohai Sea ecosystem to solve the said problems in the Hai Basin. The Hai Basin Integrated Water and Environment Management Project lessened water pollution whcih more than 20 million residents benefited.
