Please explain so I can learn how to do questions like this.

Voluntary green power purchases began through a variety of state and utility programs. Between 1999 and 2004, more than 500 utilities in 34 states began to offer their retail customers the option to buy green power. Mandates that required utilities to offer green power products were enacted in 5 states between 2001 and 2003. All but one statement describes a benefit of green power.

A Green power supports the use of renewable energy resources.
B Green power is a cheaper energy resource for the general population.
C Green power reduces greenhouse gas emissions and other pollutants.
D Green power fosters an improved living and community enviorment.