4a 部分答案
1. so that 2. Although 3. until 4. Although
4b 部分答案
1. You should practice speaking in front of the class.
2. You should talk to your sister so that you can say you're sorry.
3. You should explain that you don't mind her phoning all evening. However, she should let you give your friend a call.
4. You could tell him that this makes you unhappy so that he will return them soon next time.
5. You should communicate with them.
(答案仅供参考)