Greater use of solar electric systems benefits the environment because it
(1) depends on the greater use of fossil fuels
(2) conserves nonrenewable resources
(3) produces gases that cause global warming
(4) reduces the need for the ozone shield

i think its choice 4, am i correct?

Answer - (2) Conserves nonrenewable resources.

Reasoning - So lets pay close attention to the question as it has stated (Solar electric system benefits environment) as it means solar which is sun power which already gives a hint that we need to save the environment and try to conserve. So Greater use of the solar can help conserves nonrenewable resource which in this case is fossil fuels. 

The higher you go up the less oxygen there is