Ask your mum/dad.
Student A:Can I go to a friend's birthday party?
No, you have a lot of homework.
Student B:Can I sleep over at my friend's house?
No, you have a test tomorrow.
Ask your friend
Student A: Can I use your phone?
No, I need it.
Student B: Can I use your bike?
No, I have an important match.
Ask your teacher
Student A:Can I use the toilet?
No, but you can use it after the lesson
Student B: Can I phone my mom?
No, it is too late.