Answer:
Slavery in the U.S. caused people to create the Underground Railroad.
The simple predicate is will be ready, because it is explaining what dinner is.
Yes, Because the part of the sentence "Although it is pretty" won't be able to function on it's own as a proper sentence. However the sentence "winter isn't as pretty as fall", Is a independent clause at the end of the sentence. Hope I helped, Look at the images, It will help! :D