1.Because it was raining, we cancelled the picnic.

2.She is very kind, so my mother likes her.

3. Her childrn had dropped her key on the road, so it was lost.

4. The picnic is beautiful, so I like it.

5.Because of the terrible traffic, we didn't arrive until  seven o'clock.

6.She found the exam easy, so she had during the course.

7.We has to hurry indoors, because it was raining.

8.He is tall, so he can reach the book on the shelf.

=>
1. Because it was raining, we cancelled the picnic.
2. My mother likes her because she is very kind.
3. Her key was lost as/since her children had dropped it on the road.
Her children had dropped her key on the road, so it was lost.
4. I like this picture because it's beautiful.
5. We didn't arrive until seven o'clock because the traffic was terrible.
6. She found the exam easy because she had worked hard during the course.
7. We had to hurry indoors because it was raining.
8. Because he is tall, he can reach the book on the shelf.