A sun-starved Norwegian town has finally seen the light--by installing giant mirrors on the surrounding mountains to reflect rays onto its market square. The small town of Rjukan sits deep in the narrow Vestfjord Valley,in the Telemark region south-west of Oslo. The towering peaks that surround it rise to almost 2,000 meters above sea level and block out the sunlight for half the year, meaning Rjukan residents live in a permanent shadow from September to March. But all that changed this week, with the official launch of a project first proposed a century ago. Three high-tech mirrors,with a combined reflective surface of 50 square meters, have been put into operation on a ridge  on Gaustatoppen mountain,brightening up the previously gloomy town center by _ it with up to 600 square meters of sunlight. Twenty-first century technology has made the $850, 000 project possible, with heliostats--computer-powered mirrors--shifting every 10 seconds to track the movements of the sun during the day. But the idea to lighten up the dark town actually dates back 100 years. Rjukan was originally founded as a company town for Norsk Hydro, which set up a fertilizer plant here to make use of the hydro power from the nearby 104 meter Rjukanfossen waterfall. The story goes that the aluminum  and renewable energy company's founder,Sam Eyde,wanted a way to brighten up the existence of his shadowed 1aborers--and also to make them work more effectively during the winter. The local newspaper published a suggestion by local bookkeeper Oskar Kittelsen to use a mirror to reflect sunlight onto the town,and Eyde picked up on the idea. Technological limitations of the day meant the plan never came to fruition,however, and instead northern Europe's first cable car was built in 1928 to give Rjukan residents sunlight exposure at the top of the mountain. Norsk Hydro set up Rjukan because  _  .
there were quantities of cheaper labors there existed large amounts of hydro power it was very convenient to use water there was rich aluminum and water resources
Question: A sun-starved Norwegian town has finally seen the light--by installing giant mirrors on the surrounding mountains to reflect rays onto its market square. The small town of Rjukan sits deep in the narrow Vestfjord Valley,in the Telemark region south-west of Oslo. The towering peaks that surround it rise to almost 2,000 meters above sea level and block out the sunlight for half the year, meaning Rjukan residents live in a permanent shadow from September to March. But all that changed this week, with the official launch of a project first proposed a century ago. Three high-tech mirrors,with a combined reflective surface of 50 square meters, have been put into operation on a ridge  on Gaustatoppen mountain,brightening up the previously gloomy town center by _ it with up to 600 square meters of sunlight. Twenty-first century technology has made the $850, 000 project possible, with heliostats--computer-powered mirrors--shifting every 10 seconds to track the movements of the sun during the day. But the idea to lighten up the dark town actually dates back 100 years. Rjukan was originally founded as a company town for Norsk Hydro, which set up a fertilizer plant here to make use of the hydro power from the nearby 104 meter Rjukanfossen waterfall. The story goes that the aluminum  and renewable energy company's founder,Sam Eyde,wanted a way to brighten up the existence of his shadowed 1aborers--and also to make them work more effectively during the winter. The local newspaper published a suggestion by local bookkeeper Oskar Kittelsen to use a mirror to reflect sunlight onto the town,and Eyde picked up on the idea. Technological limitations of the day meant the plan never came to fruition,however, and instead northern Europe's first cable car was built in 1928 to give Rjukan residents sunlight exposure at the top of the mountain. Norsk Hydro set up Rjukan because  _  .
A. there were quantities of cheaper labors
B. there existed large amounts of hydro power
C. it was very convenient to use water
D. there was rich aluminum and water resources
Answer: