According to the article, when a homeowner puts in a solar roof, her worries about blackouts or power rates might be over. Why might that be true
A、Solar power may be less expensive and more reliable than power supplied by utility companies.
B．Her roof won't leak with the heavy solar panels on top of the roof.
C．Putting in a solar roof is still an expensive preposition.
D．Super-efficient appliances use less electricity than regular appliances.