What is one characteristic of solar cells? 

A)  They are primarily composed of metal. 
B)  They are quick to install. 
C)  They emit moderate amounts of carbon dioxide. 
D)  Expansion of a system of solar cells is difficult.

Solar Cells

Instruments that directly transform sunlight into electrical energy via the photovoltaic effect.

Carbon Dioxide

This substance is a transparent, unscented gas generated through the combustion of carbon and organic materials as well as through respiration, and it is a naturally occurring part of the atmosphere absorbed by plants for photosynthesis.