A、Because they outnumbered the Persians. B、Because they were attacked by the Persians. C、Because two ships became entangled with

From the earliest days, people have wanted to keep some record of their achievements. Thus they build monuments, or they tell stories from parents to children, or they write things down. To give shape to the stories, to show how events related to one another, ancient people began to write what we call histories. In both Greek and Latin, the word "historia" means a story or a narrative. Historians were regarded as those who told the story of the past.
   One of the earliest historians, a Greek named Herodotus, always tried to make sure that information was as accurate as possible. Herodotus lived in the 400’s B.C. He wrote a detailed account of the Persian Wars, the great struggle between the Greeks and the Persians that had taken place in the years before he was born.
   A great deal of our information about these wars exists only because Herodotus found it out and wrote it down. Here, to give one example, is his account of how the battle of Salamis began. This was a naval battle at which the Athenian ships defeated the Persians that had taken place in the year 480 B.C. It was one of the turning points of the war, and the question was how the Greeks, badly outnumbered, dared to fight. Here is how Herodotus explained it:
   Themistocles, the Athenian leader, told them to board their ships, whereupon the Greeks put to sea. The fleet had hardly left shore when they were attacked by the Persians. At once, most of the Greeks began to retreat, and were about to touch land again when one of the Athenian captains shot forward and charged one of the enemy. The two ships became entangled, and could not be separated. At this the rest of the Greek fleet came up to help, and the battle began.
   Ever since Herodotus, historians have recovered and preserved information about past events that otherwise would have been lost. Modern historians have continued to look for new information which helps us understand the past more clearly and more accurately.  The usefulness of historians and their works has been recognized by a number of American Presidents, who have made professional historians part of their White House staffs.
15.Which of the following is NOT mentioned as one of the ways people used to keep record of their achievements?
16.Which of the following is NOT true about Herodotus?
17.How did the Greeks dare to fight according to Herodotus?
18.In what way do American Presidents recognize the usefulness of historians and their works?