A. I missed the bus so I was late
I was late, because I missed the bus.
b. He always passes his exams because he works very hard.
He works very hard so he always passed his exams.
c. We didn t like the shop assistant so we didn t buy anything.
We didn't buy anything, because we didn't like the shop assistant.
d. We didn t go for a walk because the weather was nasty.
The weather was nasty so we didn't go for a walk.
Mam nadzieję, że o to chodzilo ;)