Read the following article and select the best answer. Article: Read the following interview with Dr John Bass, an international shark specialist who has spent many years studying sharks: First of all, doctor, are all sharks dangerous? No, they aren't. There are about 250 different kinds of sharks, but fewer than 30 of them are dangerous to humans. Certain sharks are very aggressive and we should fear them, but the danger of shark attacks is much lower than most people think. So which sharks are dangerous? The Great White shark is the most dangerous. Then there is the Tiger shark, which other sharks are afraid of, and the Blue shark. Both of them are very fast and dangerous. Which are the biggest and smallest sharks? The Whale shark is the biggest shark in the world. It grows up to 15 m in length and weighs as much as six large cars. The smallest shark, which is found near prefix = st1 /Japan, could fit into the palm of your hand because it is only 15-20 cm long. Do all sharks have teeth ? Yes, they do. Most sharks have hundreds, sometimes even thousands, of sharp teeth. These are arranged in rows of four or more. They fit quite loosely in the jaw. When the front ones break off or fall out, spare teeth move forwards from the rows behind: Sharks get a new set of teeth every two weeks. In 10 years, a Tiger may lose as many as 24,000 teeth! That's lots of teeth! What kind of food do sharks eat? Most sharks feed on small fish, and they keep the oceans healthy by eating sick and injured fish. However, hungry sharks will eat almost anything, including smaller sharks and even rubbish. Inside one Tiger shark which was found, there was a tin can, a bicycle tyre , a leather wallet and an alarm clock! And how do sharks find their food, doctor? A shark's sense of smell is excellent. It will follow the smell of blood across thousands of metres of ocean. They also see well, and they have good hearing. Sharks can feel movement in water very easily too, and it is possible for them to feel a fish moving as far as 30 m away. Question: Sharks are helpful to us as _ . - ocean cleaners - small shark feeders - big eaters - fish hunters
ocean cleaners

Read the following article and select the best answer. Article: Being an astronaut sounds cool, doesn't it?In space, they get to do some pretty amazing things, like floating in zero gravity. However,there are also plenty of things that astronauts can't do because of their weightless environment, and that's very sad. What's worse, they can't even let their sadness show--because it's impossible to cry in zero gravity. Of course, astronauts can still produce tears. But crying is much more difficult in space,reported The Atlantic in January. Without gravity, tears don't flow downward out of the eyes like they do here on Earth. This means that when you cry in space, your tears have nowhere to go--they just stick to your eyes. In May 2011, astronaut Andrew Feustel experienced this during one of his spacewalks."Tears," he said, "don't fall off your eye... They just kind of stay there." Besides making your vision unclear, this can also cause physical pain. Back on Earth, tears are supposed to bring comfort to the eyes.But that's not the case in space.The space environment dries out astronauts' eyes, and when tears suddenly wet the eyes, it can cause pain rather than comfort. "My right eye is painful like crazy." Feustel told his teammate during the walk. Since gravity doesn't work in space, astronauts need some extra help to get rid of the tears.Feustel chose to rub his eyes against his helmet to wipe the tears away. Another choice is to just wait--"When the tears get big enough they simply break free of the eye and float around,"astronaut Ron Parise told The Atlantic. There are lots of small things--things like crying--that we are so used to on Earth. We usually take them for granted, until they become a problem in a totally different environment,like space. There, astronauts can't talk to each other directly. They also can't eat or drink in normal ways. They can't even burp , because there is no gravity to hold the food down in their stomach. If they do burp, they just end up throwing up everything in their stomach,according to the UK National Space Center. Thus, perhaps it's... Question: What effect do tears have on astronauts? - They cause physical pain. - They bring comfort to them. - They make their vision clearer. - They float around and cause trouble.
They cause physical pain.

Read the following article and select the best answer. Article: In the mid-1950s, I was a somewhat bored early-adolescent male student who believed that _ . One day, this approach threw me into embarrassment In Mrs. Totten's eighth-grade math class at Central Avenue School in Anderson, Indiana, we were learning to add and subtract decimals . Our teacher typically assigned daily homework, which would be recited in class the following day. On most days, our grades were based on our oral answer to homework questions. Mrs. Totten usually walked up and down the rows of desks requesting answers from student after student in the order the questions had appeared on our homework sheets. She would start either at the front or the back of the classroom and work toward the other end. Since I was seated near the middle of about 35 students, it was easy to figure out which questions I might have to answer. This particular time, I had completed my usual two or three problems according to my calculations. What I failed to expect was that several students were absent, which threw off my estimate. As Mrs. Totten made her way from the beginning of the class,I desperately tried to determine which math problem I would get. I tried to work it out before she got to me, but I had brain freeze and couldn't function. When Mrs. Totten reached my desk,she asked what answer I'd got for problem No. 14. "I...I didn't get anything," I answered,and my face felt warm. "Correct," she said. It turned out that the correct answer was zero. What did I learn that day? First, always do all your homework. Second, in real life it isn't always what you say but how you say it that matters. Third,I would never make it as a mathematician. If I could choose one school day that taught me the most, it would be that one. Question: The author failed to get the questions he had expected because _ . - the class didn't begin as usual - several students didn't come to school - he didn't try hard to make his estimate - Mrs. Totten didn't start from the back of the class
several students didn't come to school