wet roll of paper towels should get moldy in a couple of days depending on the temperature of the room even in a bag so i suggest you just throw it away. But if you do need it then put it in the fridge because mold hates the cold weather, it thrives in warm weather. If you do that then you should have enough time to use it.
b and d are out, the variables are changed. a would be a repetition, not a replication. c uses the same method and variables with a different control group
