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hoped to become a good teacher. This year he left the college and began to work in a middle school. He likes
his students and is strict (严格的) with them. He does his best to make his classes lively and interesting.
One day he carefully explained a chemical reaction (反应) to the students of Grade 2 in the chemistry
lab.
"Be careful, everyone," he said loudly. "Before I make the experiment, there're twenty five atoms of
carbon (碳原子), but after I finish it, there're twenty four atoms of carbon left!" He stopped to watch the
classroom and hoped his students would go on explaining it. But the young men looked at each other and
nobody answered him. He had to ask, "What happens? What makes the atom lost?"
The classroom was very quiet and none of the students looked at their teacher. "Who can tell us where
it has gone?" Suddenly a soft voice came from the back row, "We did not see anybody leave the lab!"
B. he couldn't do anything except teaching
C. he hoped to become a good teacher
D. he did well in all his subjects
B. his students wouldn't be afraid of him
C. his students carefully watched him making the experiment
D. his students could do well in chemistry
B. his students could find the atom of carbon
C. his students could count (数) the atoms of carbon
D. his students could make the experiment
B. they didn't understand their teacher
C. the chemical reaction was too complicated
D. they all wanted to drop the subject
B. the student in the back row didn't watch her teacher carefully
C. the student in the back row hadn't learned chemistry before
D. Charlie failed in making the experiment
He has many friends, but ________ of them can give him any help this time.
[ ]
Is bottled water better for you than tap? Or should you choose vitamin-enriched water? Experts say, skip it all． None of these products is likely to make you any healthier． Below, we look at four major myths about the benefits of drinking water． 71 Experts say there’s an easy way to judge． If you are not thirsty, your fluid intake is likely “just right”
Myth No 1: Drink eight glasses each day．
Scientists say there’s no clear health benefit of drinking so much water a day． 72 “Nobody really knows,” says Dr． Stanley Goldfarb, a kidney expert at the University of Pennsylvania．
Myth No．2：Lots of water equals healthier skin．
The body is already 60 percent water． 73 Adding a few extra glasses of water each day has a limited effect． “It’s such a tiny part of what’s in the body,” says Goldfarb． “ It’s very unlikely that one’s getting any benefit．”
Myth No．3: 74
A more accurate statement may be: Drinking water is a helpful tool for dieters． “Water is a great strategy for dieters because it has no calories,” says Madeline Fernstrom of the University of Pittsburgh． “So you can keep your mouth busy without food and get a sense of satisfaction．” But water is not magical, she adds． “Other zero-calorie options such as diet sodas are fine, too．”
Myth No． 4: It’s easy to get dehydrated（脱水的） during a workout．
Dehydration sets in when a person has lost 2 percent of his or her body weight． 75 “It’s also obvious that individuals in hot, dry climates have an increased need for water,” says Goldfarb． “But for a walk in the park, no water bottle is necessary．”
A. So where does the standard advice come from?
B. But it’s unclear whether these changes are clinically significant．
C. So for a 200-pound man, this means losing 4 pounds of water．
D. Drinking extra water leads to weight loss．
E. Drink as much water as you can．
F. So, if you take a 200-pound man, he’s 120 pounds of water．
G. But first, how do you know if you’re drinking enough water?
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