Scientists are discussing ways to remove excess carbon dioxide from the atmosphere by increasing the amount that is absorbed by plant life. One plan to accomplish this is to establish giant floating seaweed farms in the oceans. When the seaweed plants die, they will be disposed of by being burned for fuel. Which of the following, if true, would indicate the most serious weakness in the plan above? ['Even if seaweed farms prove effective, some people will be reluctant to switch to this new fuel.', 'Some areas of ocean in the Southern Hemisphere do not contain sufficient nutrients to support large seaweed farms.', 'Each year about seven billion tons of carbon dioxide are released into the atmosphere but only about five billion tons are absorbed by plant life.', 'When a seaweed plant is burned, it releases an amount of carbon dioxide comparable to the amount it has absorbed in its lifetime.']