16.Many rivers and lakes are poisoned.Factories produce waste and pour it into rivers and lakes

->because factories produce waste and pour it into rivers and lakes​,many rivers and lakes are poisoned

17.Plastic bags are a major source of waste.We should not throw plastic bags everywhere

->(so) Plastic bags are a major source of waste so we  should not throw plastic bags everywhere​

18.we won't hold the festival.It costs too much money

->If it didn't cost much money,we would hold the festival

19.the tortoise was running.the hare was sleeping

->(while) While the tortoise was running,the hare was sleeping

20.the girl worked hard.Her stepmother wasn't happy

->(Although) Although the girl worked hard,her stepmother wasn't happy
Tick hết điểm cho mk nha!