Sharks are generally carnivorous, but some scientists claim that they found a narrow-headed double-headed shark that uses plants as an important part of food in a certain sea area. If the following are true, which most support these scientists' findings is:. ['Researchers analyze food in their stomachs and find that half of the food composition of some narrow-headed hammerhead sharks are plants.', 'The narrow-headed double-headed shark that is artificially fed with a special feed of 90% of seagrass has gained weight during the 3-week experiment.', 'Research finds that an enzyme that can efficiently break down plants exists in the intestines of narrow-headed shark sharks, which does not exist in the intestines of other sharks.', 'The blood of the narrow-headed hammerhead shark contains a large amount of non-self-synthesized nutrients. In nature, only seaweed contains a small amount of this nutrient.']