Refer to the Department of Energy's "Guide to Renewable Energy." How does the article make a connection between geothermal heat pumps and solar systems? (A)It suggests that geothermal heat pumps cost less to install than solar panel systems with the same capacity. (B)It hints that geothermal heat pumps save homeowners more money per unit than solar panels do. (C)It points out that geothermal heat pumps and solar panel systems are built to last a long time without major repairs. (D) It explains how geothermal heat pumps have three times more efficiency than solar water heaters do.