What is the biggest disadvantage of solar electricity, or at least, why is it not used much more than it currently is? a. it’s very costly b. carbon dioxide emissions c. leads to water and air pollution d. it’s not renewable.

Well the main reason why people invented and started using electricity from solar power is because of no emissions of carbon dioxide, no water and air pollution and it is renewable. So, B,C,and D cannot be the answer.

The answer A is indeed correct. At the moment solar panels are still expensive for the power they bring. Engineers hope to bring cost of panels lower which would make solar power less cheap than oil extracting (of course, for same amount of power).