The energy crisis the world is now experiencing has prompted scientists to investigate new sources of energy. Solar power is receiving wide attention as a possible source of clean, inexpensive and abundant energy. The conversion of the sun's rays to electricity does not pollute the environment and costs only as much as the installation of solar panels to absorb the sun's rays. Admittedly, this system would not work well in a cloudy area, but in countries like the United States where sunny days are numerous, solar power could help solve the energy crisis.

Q. Circle the outline which illustrates the structure of the paragraph and underline the topic sentence: ▼ ▲ ♦ ▊.