Formulating a compound sentence

and

My friend couldn't come over to play, so I did something by myself instead.

Would you like to eat dinner now, or would you like to go for a walk first?

I forgot my homework, but my teacher said I can bring it in tomorrow for credit.

The teacher handed back our tests, but she didn't score them yet.

or

Tom drove the car, but it ran out of gas before he got to his destination.

But

So

We didn't have a ride to the park, so we played at home instead.