Here are possible fill-ins for the blanks:

1. **(1)**: "where"
2. **(2)**: "speak"
3. **(3)**: "terraced"
4. **(4)**: "colorful"
5. **(5)**: "patterns"

So the completed text would read:

"In the provinces (1) **where** there are more than 1.4 million Muong people living. They (2) **speak** Muong language which belongs to the Mon-Khmer group. However, some of them also know Kinh language. They cultivate mainly wet rice on (3) **terraced** land, watered by small brooks. They also make handicrafts and exploit forest products such (4) **colorful** mushrooms, dried fungus, ammonium to improve their living condition. Men dress in indigo pajama and women wear skirts with (5) **patterns** knitted on."