1, It has been the national day of Viet Nam since 1945
-> How long has it been  the national day of Viet Nam?
2, Hung Kings are the founders of our nation and they became the first kings of our country
-> Who  are the founders of our nation and they became the first kings of our country?
3, Must ethnic peoples in viet nam speak their own languages 
-> What do must ethnic peoples in viet nam speak?
4, In the central highlands, the biggest and tallest house in the village is the communal house 
-> What is the biggest and tallest house in the village in the central highlands?
5, They are working in a factory
-> Where are they working?
6, They went to Sapa
-> Where did they go?