Which process will decrease the level of CO2 in the atmosphere?

Question

 Which process will decrease the level of CO2 in the atmosphere?
growing trees
cutting trees
burning trees
increasing the human population

Answer 1

Since green plants consume CO₂, a process that promotes growth of green plants should reduce the level of CO₂ in the atmosphere.  Which process in the list promotes growth of green plants?  I suggest "growing trees".