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C. Plants have been using solar energy for billions of years.
D. Plants have been a source of solar energy.
32. Why do some scientists study how plants convert sunlight into carbon dioxide, and water into sugars and starches?
A. Because they want algae to produce sugars and starches.
B. Because they want green plants to become a new source of energy.
C. Because they want to turn plant sugars to a new form of energy.
D. Because they want to make photosynthesis more efficient.
33. According to the fifth paragraph, under what conditions are algae able to use solar energy to make hydrogen?
A. When there is a lot of oxygen in the air.
B. When there is no oxygen in the air.
C. When photosynthesis is taking place.
D. When enough starch is stored.
34. Researchers have met with difficulties when trying to make algae produce hydrogen efficiently. Which one of the following is one such difficulty?
A. It is not possible to remove sulfate from the environment.
B. It is not possible to work in an airfree environment to produce hydrogen.
C. It is not easy to make sugars instead of hydrogen.
D. It 1s too slow for algae to produce hydrogen when the sulfate is removed.
35. What is NOT true of algae?
A. They are easy to grow.
B. They can be a very good fuel source.
C. They are cheap to eat.
D. They can be used in many ways.
“Life Form Found” on Saturn’s Titan
Scientists say they have discovered hints of alien life on the Saturn’s moon. The discovery of a sort of life was announced after researchers at the US space agency, NASA, analyzed data from spacecraft Cassini, which pointed to,the existence of methane-based form of life on Saturn’s biggest moon.
Scientists have reportedly discovered clues showing primitive alien beings are “breathing” in Titan’s dense atmosphere filled with hydrogen.
They argue that hydrogen gets absorbed before hitting Titan’s planet-like surface covered with methane lakes and rivers. This, they say, points to the existence of some “bugs” consuming the hydrogen at the surface of the moon less than half the size of the Earth.
“We suggested hydrogen consumption because it’s the obvious gas for life to consume on Titan,similar to the way we consume oxygen on Earth,”says NASA scientist Chris McKay. “If these signs do turn out to be a sign of life, it would be doubly exciting because it would represent a second form of life independent from water-based life on Earth.”
To date,scientists have not yet detected this form of life anywhere, though there are liquid-water-based microorganisms on Earth that grow well on methane or produce it as a waste product. On Titan, where temperatures are around 90 Kelvin minus 290 degrees Farenheit),a methanebased organism would have to use a substance that is liquid as its medium for living processes, but not water itself. Water is frozen solid on Titan’s surface and much too cold to support life as we know it.