Finish the following sentence with the best choice: How to prepare to patch a bicycle tube?

Choices:
- Once you've isolated the puncture, scrape it smooth with some sandpaper until it is rough and open then apply the patching glue
- Once you've isolated the puncture, scrape it smooth with some sandpaper until it is clean and smooth then apply the patching glue

Answer:
Once you've isolated the puncture, scrape it smooth with some sandpaper until it is clean and smooth then apply the patching glue