All too often, a choice that seems sustainable turns out on closer examination to be problematic. Probably the best example is the rush to produce ethanol  for fuel from corn. Corn is a renewable resource --you can harvest it and grow more, almost limitlessly. So replacing gas with corn ethanol seems like a great idea. One might get a bit more energy out of the ethanol than that used to make it, which could still make ethanol more sustainable than gas generally, but that's not the end of the problem. Using corn to make ethanol means less corn is left to feed animals and people, which drives up the cost of food. That result leads to turning the fallow land -including, in some cases, rain forest in places such as Brazil--into farmland, which in turn gives off lots of carbon dioxide (CO) into the air. Finally, over many years, the energy benefit from burning ethanol would make up for the forest loss. But by then, climate change would have progressed so far that _ might not help. You cannot really declare any practice "sustainable" until you have done a complete life-cycle analysis of its environmental  costs. Even then, technology and public keep developing, and that development can lead to unforeseen and undesired results. The admirable goal of living sustainably requires plenty of thought on an ongoing basis. What might directly cause the loss of the forest according to the text? A) The growing demand for energy to make ethanol B) The increasing carbon dioxide in the air C) The greater need for farmland D) The big change in weather.
C

Let's face it.No one drinks die t soda  for the taste.People drink diet soda in the hope that it will help them lose weight or at least keep them from gaining it.Yet it seems to have exactly the opposite effect, according to a new study. Researchers from the University of Texas said those who drank two or more diet sodas a day had waist  size increases that were six times greater than those of people who didn't drink diet soda."What we saw was that the more diet sodas a person drank, the more weight they were likely to gain," said Sharon Fowler. The study was based on data from 474 participants in a large, ongoing research project, where the participants were followed for nearly l0 years. While the findings are surprising, they also offer some explanations. Nutrition  expert, Melanie Rogers, who works with overweight patients in New York, has found that when patients are switched  from regular to diet soda, they don't lose weight at all."We weren't seeing weight loss necessarily, and that was confusing to us," said Rogers. So why would diet soda cause weight gain? No one knows for sure yet, but it could be that people think they can eat more if they drink diet soda, and so over-compensate  for the missing calories( ). A related study found some sweeteners   raised blood sugar levels in some mice." Data from this and other potential studies suggest that the promotion of diet sodas and artificial  sweeteners may be risky," said study researcher Helen P.Hazuda, professor at the University of Texas's school of medicine. Theymay be free of calories, but not of consequences. The new study suggests that drinking diet soda   _  . A) helps people to be healthier B) causes people to become heavier C) offers people more calories D) makes people much thinner
B

He is a real turtle . Someone who always moves very slowly. She is such a sheep. A follower; someone who can't think for him or herself. He's being an ostrich . Someone who hides his/her head in the sand and refuses to face problems or reality. He's a lamb. A gentle, patient, understanding person. Nice and considerate. What a crab  he is! A grouchy  person; someone who is often angry and in a bad mood. If a person is like a turtle, which of these is most likely to be a problem to him or her? A) Keeping the house clean. B) Learning a new language. C) Getting to school on time. D) Saving money for future use.
C

Just 10 years ago, I sat across the desk from a doctor. "Yes," he said, "there is something wrong with the left, upper lobe . You have a moderately advanced case... You'll have to give up work at once and go to bed. Later on, we'll see." Feeling like a man who is in midcareer has suddenly been placed under sentence of death, I left the doctor's office, walked over to the park, and sat down on a bench. I needed to think. In the next 3 days, I cleared up my affairs, then I went home, got into bed, and set my watch to tick off not the minutes, but the months. Two years later, I left my bed and began the long climb back. It was another year before I made it. I speak of this experience because _ that passed so slowly taught me what to value and what to believe. I realise now that this world I'm living in is not my oyster  to be opened but my opportunity to be grasped. Each day, to me, is a precious thing. The sun comes up and presents me with 24 brandnew, wonderful hours--not to pass, but to fill. I've learned to appreciate those little, allimportant things I never thought I had the time to notice before:the play of light on running water, the music of the wind in my favourite pine tree. I seem now to see and hear and feel with some of the recovered freshness of childhood. How well, for instance, I recall the touch of the springy earth under my feet the day I first stepped upon it after the years in bed. Frequently, I sit back and say to myself, "Let me make note of this moment I'm living right now, because in it I'm well, happy and hard at work doing what I like best to do. It won't always be like this, so while it is, I'll make the most of it--and afterwards,  I remember--and be grateful. All this, I owe to that long time spent on the sidelines of life." Which word can best describe the author's feeling after visiting the doctor? A) Hopeless. B) Curious. C) Confused. D) Energetic.

A