The carbon dioxide absorbed by plants is returned to the atmosphere when; plants break down the sugar for energy.
animals eat the plants and break down the sugar for energy.
plants die and decompose.
All of these choices are correct.

Which of the following statements best characterizes changes to agriculture in the united states since 1900? a. increased mechanization has reduced the need for labor.b. increased mechanization has increased the need for water, thereby increasing the need for labor.increased mechanization has increased the use of land, thereby increasing the need for labor.d. increased mechanization has increased food production, thereby increasing the need for labor. select the best answer from the choices provided.