Compound Sentences

Does this sentence need a comma?
I wanted to go to the store but I decided to stay home instead.

Does this sentence need a comma?
I went to dance and then went home.

Does this sentence need a comma? Should I go to the mall or the movies?

Does this sentence need a comma? She said you were sick but I think you're just lazy.

Does this sentence need a comma?
Every day was happy and every night was peaceful.

The weather today will be cool ____ rainy.

Complete the sentence with the coordinating conjunction that makes sense.
Andy plays the violin well, _____ the trumpet is his favorite instrument.

You may have soup, ____ you may have salad.

Complete the sentence with the coordinating conjunction that makes sense: Eric got an A on the spelling test, _____ he had studied hard.

Complete the sentence with the coordinating conjunction that makes sense: Mom wanted a scrapbook of our trip, _____ she took many pictures.