Read the Passage and answer the questions

Walls and wall building have played a very important role in Chinese culture. Not only towns and villages, the houses and the temples within them were somehow walled. The houses also had no windows overlooking the street, thus giving the feeling of wandering around a huge maze. Thus, a great and extremely laborious task of constructing a wall that runs the length of the country must not have seemed such an absurdity.

Various dynasties contributed to constructing and refurbishing of a wall whose foundations had been laid many centuries ago. It was during the $$4^{th}$$ and $$3^{rd}$$ century B.C. That each warring states like Chin, the Chao and the Yen started building walls to protect their kingdoms both against one another and against northern nomads. They also laid foundations on which Chin Shih Huang Di would build his first continuous Great Wall.

Throughout the centuries many settlements were established along the border. The garrison troops were instructed to reclaim wasteland and to plant crops in, it, build roads and canals. All these undertakings greatly helped increase the country's trade with many remote areas and also with southern central, and western parts of Asia.