[填空题]The life form between 3.8 and 2.5 billion years ago was ______.

[填空题]The life form between 3.8 and 2.5 billion years ago was ______.

[单项选择]What do we know about life ten or fifteen years ago
A. It was harder for people to get in touch online
B. The Internet first came into use then
C. People enjoyed life more

[简答题]生活型(life form)

[单项选择]
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
A. They have found methane-based life on Saturn.
B. They have found a new moon orbiting Saturn.
C. They have found methane-based life on Titan.
D. They have found earthlike life on a Saturn’s moon.

[单项选择] 第三篇"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
A. Water-based life on it.
B. Methane—based life on its biggest moon.
C. A new moon moving around it.
D. Earthlike life on its biggest moon.

[单项选择]
Years ago, social scientists introduced the broken-windows theory of crime control, which assumed that if a neighborhood looked orderly and cared for — with no broken windows — potential wrongdoers would be dissuaded from committing crimes there. Now psychologists have proposed a similar theory, which suggests that people can be induced to behave morally when their environment smells as clean as it looks. It’s the Macbeth principle of morality, says Katie Liljenquist, professor of organizational leadership at Brigham Young University’s Marriott School of Management and lead author of the new study, to be published in Psychological Science. "There is a strong link between moral and physical purity that people associate at a core level. People feel contaminated(受污染的) by immoral choices and try to wash away their sins," says Liljenquist. "To some degree, washing actually is effective in relieving guil
A. $4.
B. $9.5.
C. $2.5.
D. $5.5.