1)we spent the whole day in the garden because  the weather was lovely 

2)he can't go to school today because  he has a toothache

3)i can't play basketball because iam not tall

4)she must stay in bed because she is ill

5)we can't swim in this part of the river the water is highly polluted 

6)they couldn't keep on clearing the beach because it rained heavily.

1. Because the weather was lovely, we spent the whole day in the garden.

2. Because he has a toothache, he can't go to school.

3. Because my height is not enough, I can't play basketball.

4. Because she was ill, she must stay in bed.

5. Because the water is highly polluted, we can't swim in this part of the river.

6. Because the rain was heavy, they couldn't keep on clearing the beach.