Best answer gets ! .
which of the following is caused by natural processes?

the hole in the ozone
global warming
the greenhouse effect
acid rain

The green house effect is the only naturally occurring  problem.
 The greenhouse effect is an increase in the average temperature of the Earth.  It happens because certain gases absorb infrared heat that would normally be radiated into space.  Infrared light is what you feel as heat from heat lamps used in restaurants to keep french fries hot.  It also causes the heat you feel from ordinary light bulbs.  Since carbon dioxide absorbs this heat, the more carbon dioxide there is in the atmosphere, the warmer the air will be.  If the air gets too hot, the balance of life will be disrupted.  Species of plants and animals will die.  The food chain could be upset.  This would cause many serious problems worldwide.