更多"We don’t see or hear them, but ever"的相关试题:
[填空题]We don’t see or hear them, but every day they quietly go about their work--filtering and cleansing our rivers and streams. And if we don’t act soon, they’ll disappear from the workforce just when we need them most. I am talking about pigtoes, monkeyface, pink heelsplitter and purple wartyback--freshwater mussels (贻贝) with funny names that belie the seriousness of their labors. (41) .
One mussel alone can cleanse as much as a gallon of water per hour. Add up the work of a whole mussel community, and you get a virtual water treatment plant. According to Ethan Nedeau, an expert on the freshwater mussels of New England, even half the population of mussels at work in a one-half mile segment of New Hampshire’s Ashuelot River can help cleanse more than 11.2 million gallons of water a day--roughly the quantity of household water used by 112 000 people.
(42) . Today 69 percent of US freshwater mussel species are to some degree at risk of extinction or already extin
[填空题]
Almost every day we see something in the papers about the latest exciting developments in the space race. Photographs are regularly flashed to the earth from thousands and even millions of miles away. They are printed in our newspapers and shown on our television screens as a visible proof of the man’s newest achievements. The photographs neatly sum up the results of these massive efforts to ’ conquer space’ and at the same time they exposed the absurdity of the undertaking. All we can see is an indistinguishable blob that is supposed to represent a planet seen from several thousand miles away. We are going to end up with a little moon-dust and a few stones which will be put behind glass in some museum. (41)__________
(42)__________It is just an extension of the race for power on earth. Only the wealthiest nations can compete and they do so in the name of pure scientific research. But in reality, all they are interested in is power and prestige. They wan
