The correct answer is C) dispersants. Dispersants are not usually allowed for cleaning up oil spills, as they are considered a chemical method that can have harmful environmental impacts. Instead, mechanical methods like skimmers (A) are the preferred approach for containing and removing oil from the water's surface. Other natural sorbents like sawdust (B) and straw (D) may be used, but dispersants that break up the oil are generally not permitted except in specific situations approved by regulators.