In the year 480 BC the Greek allies faced invasion by the King of Persia,Xerxes,who commanded a huge army of about half a million men. When the Persian army marched into northern Greece,the Greek states,led by Athens and Sparta,were ill equipped to deal with the threat. The Persians were well supplied with food and weapons. Their army included infantry,cavalry,and a large navy. It seemed that they would easily defeat the Greeks. The Greek allies decided to send 10,000 men northwards to slow down the Persians,while the rest prepared to defend their homelands. A group of 300 best Spartan soldiers were chosen to lead the force going north,with Leonidas in command. Leonidas realised that the only hope of slowing the Persians would be to block the narrow passage of land at Thermopylae. The Pass of Thermopylae was the route between the mountains and the sea,and was so narrow that only a few men could get through at a time. When the Persian army arrived at Thermopylae,they found Leonidas' tiny army opposing them. The Persians attacked,but could not get through. They attacked again and again,but each time they were driven back by the Greeks,led by the fearless Spartans. Leonidas'plan worked well until a Greek traitor called Ephialtes went to Xerxes. He told the Persian king about a goat's path in the mountains that would take the Persian army past Thermopylae. When Leonidas saw the enemy crossing the mountains,he realised that he could no longer hold Thermopylae. He sent all the Greek soldiers except the 300 Spartans back to their homelands. The Spartans waited for the 500,000 Persians at the goat's path. Although hopelessly outnumbered,the Spartans fought bravely. They all died,but the other Greeks were able to get home to strengthen the defences. Why did Leonidas send most of his soldiers back to their homelands? A) Because their homelands were under attack. B) Because he found they were not brave enough. C) Because the Persians gave up attacking Thermopylae. D) Because he found it impossible to hold Thermopylae.
D
A new smart phone system under development can locate you even when you're inside a building, which GPS can't do. While the concept sounds powerful, it's not yet clear how practical it might be. The set-up, called SurroundSense, sends information from cameras and microphones--gear in the latest smart phones--to a server that produces a fingerprint of the location. "You can't tell much from any of the measurements individually, but when combined, the optical , acoustic and motion information creates a unique fingerprint of the space," said Ionut Constandache, a student in computer science. The system distinguishes between two indoor spaces in this manner: It knows that a bar is likely to be dark and noisy and people move little, sit a lot, whereas a department store will be brightly lit, contain vibrant colors, and will see a lot of people moving up and down passages. The more the system is used, the more it learns about specific places. More work is needed before the set-up would be ready for prime time, however. For now, it can't work if a person's cellphone is in a handbag or otherwise unable to employ the camera. Finally it would be best served if paired with phones that were worn on the wrist or hung around the neck. Batteries, too, are a problem. Students on the research team went out across Durham, North Carolina, with their cellphones collecting data in different types of businesses. The students mirrored the actions of the selected customers so that they would not prejudice the measurements. "We went to 51 different stores and found that SurroundSense achieved an average accuracy of about 87 percent," Constandache said. "As the system collects and analyzes more and more information about a particular site, the fingerprint becomes more precise," said Romit Roy Choudhury, professor of computer engineering. "Not only is the _ different at different locations, but also can be different at different time at the same location." The main idea of the passage is about _ . A) comparing GPS with a smart cellphone B) the development of cellphones C) a cellphone knowing where you are D) what kind of future cellphones face
C
*Question*
My oldest child, Emma, just returned to campus after a long holiday break to finish up her last period of college. These days, friends and family have begun flooding me with one question: What is she going to do after graduation? The job market is, after all, awfully tough. Just this month the Federal Reserve Bank published a study showing that "recent graduates are increasingly working in low-paid jobs or working part-time." The bright spot, according to the study, is for students who majored in STEM-- science, technology, engineering and mathematics -- areas in which recent graduates "have tended to do relatively well". But Emma is a student of the humanities at a small college. She's an American Studies major with a focus on the politics and culture of food. For quite a while, I think her field of study is so fashionable right now that I'm not the least bit worried she will find a good job. Yet the more I've thought about it, the more I've decided to be honest. "I'm not sure what Emma is going to do," I now say. "But she's gotten a great education and has really found her interest. -- and I know those things will serve her well over the course of her life." Nowadays, more and more universities and colleges are being measured by the salaries of their recent graduates. In this climate, encouraging your kid to study the humanities, seems, at best, unwise or, at worst, unconcerned with earning a living. But a college is not a vocational school. And promoting STEM subjects should not be society's only answer to helping the next generation grow in a competitive world. From the beginning, we never urged Emma to pick a college or a major with an eye on its expected return on money, as more and more families are doing. To Emma, what really matters will be something that we may not be able to measure for quite a long time: Emma's contribution to the world and how happy she is in it. The author's friends and family _ . A) are worried about Emma's safety B) have been worrying about the flood C) are concerned about Emma's future D) are worried about the job market
**Answer**
C