Question: Read the following article and select the best answer. Article: Two Chinese farmers who became an overnight hit when their heart-rending version of a famous pop song appeared on the Internet took to the stage in front of thousands of fans in Shanghai last Saturday. Wang Xu, 44,and Liu Gang, 29, sang "In the Spring" alongside the song's star composer Wang Feng, in front of about 80,000 people at the Shanghai Stadium. The audience buzzed with excitement and let out deafening cheers, the moment as they were introduced on the stage and then when Liu started the first sentence of their parts of the song. The two migrant workers became stars after singing the tearjerker song during an evening drinking session in a 6-square-meter rented room in a late August evening. A friend recorded the performance on a cell phone and posted it on the Internet. "If someday I am dead, please bury me in the spring," they sing. Wang's penetrating chorus, delivered with his eyes closed, has moved thousands to tears. Wang and Liu consider the song a true portrait of lower-class groups like themselves. "With no credit card, no girlfriend, or a home with hot water, but only a guitar, I am singing happily, on streets, under bridges or in wild country, though nobody pays attention to the music," they sing. To support his wife and two sons, Wang came to Beijing in 2000 from the countryside and has worked as a boiler man, and street peddler, before becoming a medical warehouse keeper, with a monthly pay of around 1,500 yuan. Little is left after he pays 600 yuan for rent and buys food. Liu came to Beijing in 2002. "I wanted to try my luck in the big city, " he said. He had worked as a guard, roadside peddler, and porter, but never had a stable job. Street performing was his main income, even after he married and became a father three years ago. Wang and Liu are still uncertain where their fame will lead. Wang has started learning to use a computer. They even have a micro blog account to communicate with fans. Question: Wang Xu and Liu Gang first became nationally known after _ . - they sang the song "In the Spring" with a star composer Wang Feng. - the video of them singing "In the Spring" was posted on the Internet. - they sang on streets and under bridges. - they started their micro blog.
Answer:
the video of them singing "In the Spring" was posted on the Internet.