2.Teenagers/decisions/concerning/theirlives/participate in/will/important/./

⇒Teenagers will participate in important decisions concerning their lives.
3. In spite of/poor health/her/works/twelve/a day/hours/she/./

⇒ In spite of her poor health, she works twelve hours a day .
4. My grandfather,/ten years./has been/for/retired/who/an astronaut, /be/used to/

⇒ My grandfather, who used to be an astronaut, has been retired for ten years now. 
5. a workshop/ Bat Trang/ in/ Nam's family/owns

⇒ Nam's family owns a workshop in Bat Trang.
6. People/ that/ the / believe/ in/Phong Nha/ is/ biggest/ cave/ Viet Nam.

⇒ People believe that Phong Nha is the biggest cave in Vietnam.
7. I/ study /, / harder /I/ pass / will/the/ written examination / If.

⇒ If I study harder, I will pass the written examination.

8. Câu này ≡ câu 3 
9.Câu này ≡ câu 4
10.Nowadays,/there/varieties of/all over the world/English/are/such as/and /British English/AmericanEnglish/Indian English.
⇒ Nowadays, there are many varieties of English all over the world such as British English, Australia English, American English, Indian English.