Could I ...? / Do you mind if I ...?

It's a hot day. You want your classmate to open the door.

You go to your friend's house and it's so beautiful. Ask him/her to look around.

You have an exam but you forgot your pen. Ask if you can borrow one.

It's freezing cold and your partner has an extra coat. Ask him/her if you can use it.

Your friend asks you to drive him/her to the subway.

You want to enter a friend's bathroom.

You need money. Ask your partner if he/she can lend you some money.