1 My ankle hurt. I didn't take a painkiller. 2 Doctors prescribed too many antibiotics. Bacteria became resistant to them. 3 I used a lot of energy last month. I received a very high electricity bill. 4 I sprained my ankle. I went to school by car. 5 Guards didn't protect the research centre well enough. Activists broke in. 6 You got out of shape. You hadn't exercised regularly.
1. because/but (zależnie od kontekstu)
2. so
3. so
4. so
5. and/so
6. because