The construction work of the Great Wall began .
举一反三
- the construction of the first Great Wall
- The construction of the Great Wall involved 19 states.
- The construction of the Great Wall took more than_________ and involved ________ .
- The construction of the Great Wall took more than 2000 years and involved 19 states.
- Which of the following were likely used in the construction of the Qin Era Great Wall? （ ） A: Dirt B: Wood C: Stone D: Brick