Li's English book weighs 3 pounds, her math book weighs 5 pounds, her history book weighs 4 pounds, and her science book weighs 6 pounds.How many different combinations of one or more books can Li pack in her backpack so that the total weight of the books is 12 pounds or less?
  1. 9

  2. 10

  3. 11

  4. 12

  5. 18