can someone help me?
12. The carbon dioxide levels decrease once a year because (1 point)
the air purifiers humans use eliminate them. on Earth Day, the clean-up efforts remove them. the tilt of Earth allows plants to be more productive. businesses closing for the holidays produce less waste.

Question

can someone help me?
12.   The carbon dioxide levels decrease once a year because  (1 point)
the air purifiers humans use eliminate them. on Earth Day, the clean-up efforts remove them. the tilt of Earth allows plants to be more productive. businesses closing for the holidays produce less waste.

anonymous · Answer

the tilt of Earth allows plants to be more productive

anonymous · Answer

think about this, 3 of the options are man-made phenomena that have only recently been taking place, only 1 is a natural phenomena as @70vebelle has answered.