Do you have a favorite kind of batting? I‘ve used both A & C. They both worked fine for me. It's up to you what you use. No choice is right or wrong, it's what you prefer to work with that's important. Try quilting small projects like wall hangings, mug rugs, table runners and so on with different types of batting to see which suits you and your machine best. I personally use whatever I have on hand, which might be cotton, poly, or even a fleece blanket! A will give you a fluffier quilt. B will give you a thinner more dense quilt and C is for a full size quilt but you can also cut it to the right size. C is my favorite