In this task, you're given an article and an answer. Your task is to generate the question for the answer based on the given article.

Example input: Article: There are a lot of public libraries in Britain. These libraries have more than one hundred and fifteen million books, not including those libraries of public schools. Public libraries not only lend books, music records but also help children, patients in hospitals and others to get special play readings, film shows and so on. The first public libraries were founded in about the year 1850. Today's public libraries usually have a reading-room, a lending room and a reference room. The greatest and most famous library in Britain is that of the British Library in London. It was founded in 1973 and has over 10, 000, 000 books. It has nearly every magazine, newspaper and book published in Britain and other parts across the world.
Answer: 10,000,000 or less.
Example output: How many books are there in the British Library?
Example explanation: In the Article, 10,000,000 is mentioned for the number of books available in the British Library, so this is a good question.
Q: Article: Mark Twain's works are enjoyed worldwide. His real name was Samuel Langhorne Clemens and he was born on November 30th, 1835, in the village of Florida, Monroe County, Missouri. After his father's death in 1847, Twain was apprenticed to a printer and wrote for his brother's newspaper. Later, Twain worked as a licensed Mississippi riverboat pilot, adopting his name from the call ('Mark twain!'--meaning by the mark of two fathoms) used when sounding river shallows. After the Civil War, Clemens brought an end to the steamboat traffic and moved to Virginia City. On February 3, 1863, 'Mark Twain' was born when he signed a humorous travel account with his new name. In 1864, Twain went to San Francisco to work as a reporter. He traveled in France and Italy and his experience were recorded in 1869 in the Innocents Abroad, which brought him wide popularity, and made fun at both American and European prejudices and manners. In 1870 he married Olivia Langdon. Together they relocated to Harford a year later. Meanwhile, Twain continued to lecture in the United States and England. Between 1876 and 1884 he published several masterpieces, including Tom Sawyer, the Prince and the Pauper, Life on the Mississippi, and Huckleberry Finn. In the 1890s, Twain lost most of his earnings in financial speculations and in the downhill of his own publishing firm. The death of his wife and his second daughter brought a sense of gloom in the author's later years, which is seen in writings and his autobiography. Twain died on April 21st, 1910.
Answer: Life on the Mississippi
A:
Which of the following works made Mark Twain begin to be popular?