阅读下列短文，从每题所给的四个选项中，选出最佳答案
A
"Mark Twain" was the name used by Samuel Langhorne Clemens (1835-1910) when he wrote books. His father was a lawyer, but a poor one, who lived at Florida, Missouri. The family was so poor that Samuel did not receive much teaching. He had to learn all that he could from the people whom he met. His father died when he was very young, and then there was even less money than before.
Many of the men in this part of America worked in the ships on the great River Mississippi, and he did this himself at one time (1857).
Where did he find the name "Mark Twain"? It came from the great river itself. It was part of one of the cries used by men who worked in the ships. When a man called "By the mark twain!" he meant that the river was "tw
