Refer to the Department of Energy's "Guide to Renewable Energy." What is the author's purpose in mentioning the types of renewable energy systems?

to prove that renewable energy systems work effectively to save energy and money

to introduce three systems homeowners can install to save energy and money

to describe how each energy system is installed

to compare renewable systems to see which one works best

Which two elements does this excerpt from a christmas carol by charles dickens contain? "a small matter," said the ghost, “to make these silly folks so full of gratitude." "small! " echoed scrooge. the spirit signed to him to listen to the two apprentices, who were pouring out their hearts in praise of fezziwig: and when he had done so, said, "why! is it not? he has spent but a few pounds of your mortal money: three or four perhaps. is that so much that he deserves this praise? " "it isn’t that," said scrooge, heated by the remark, and speaking unconsciously like his former, not his latter, self. "it isn't that, spirit. he has the power to render us happy or unhappy; to make our service light or burdensome; a pleasure or a toil. say that his power lies in words and looks; in things so slight and insignificant that it is impossible to add and count ’em up: what then? the happiness he gives, is quite as great as if it cost a fortune." he felt the spirit's glance, and stopped. "what is the matter? " asked the ghost. "nothing particular," said scrooge. "something, i think? " the ghost insisted. "no," said scrooge, "no. i should like to be able to say a word or two to my clerk just now. that's all."