题目内容
A．40 students attended the class.B．There were 33 students in the class.C．18 boys should
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A．Please open the door.B．Don't open the door.C．She is not sure whether to open the door
Section B
Directions: This section is to test your ability to understand short dialogues. There are 5 recorded dialogues in it. After each dialogue, there is a recorded question. The dialogues and questions will be spoken two times. When you hear a question, you should decide on the correct answer from the 4 choices marked A, B, C and D.
(6)
《政府采购法》规定，政府采购合同应当采用书面形式。即采用口头形式或其他形式订立的政府采购合同都是无效的。政府采购合同中必须包括必备条款的内容，否则合同无效。 ()
With Mars the scientific benefits are perhaps higher than they have ever been. The issue of whether life ever existed on the planet, and whether it persists to this day, has been highlighted by accumulating evidence that Mars once had abundant liquid water and by the controversy over suggestions that fossils of bacteria rode to Earth on a rock ejected from Mars during its early history. A definite answer about life on Mars, past or present, would give researchers invaluable data about the range of conditions under which a planet can generate the complex chemistry that leads to life. The revelation that life arose independently on Mars and on Earth would provide the first concrete clue in one of the deepest mysteries in all of science: how prevalent is life in our galaxy？
One of the reasons why the idea of sending people to Mars strikes a chord in so many people is that it is already possible—the U.S. has the money and the fundamental technology needed to do it. More important, recent discoveries about the planet's environment in the distant past have presented a clear and compelling scientific incentive for sending people: to search for evidence of life. The thesis that liquid water was once stable on Mars has been strengthened by aerial photographs taken last year that showed what appeared to be a drainage channel cut deeply by water flowing for hundreds if not thousands of years.
A thorough hunt for any life on Mars that might be hanging on—despite the present deficit of water—would also have to be undertaken by humans, according to some experts. Such life will be hidden and probably tiny. "Finding it will require surveying vast tracts of territory," one expert explains. "It will require the ability to cover long distances and adapt to different conditions." Robots might be up to the task sometime in the distant future, making human explorers redundant, he concedes. But relying on them to survey Mars during periodical missions to the planet would take a very long time—"decades if not centuries," he believes.
Which of the following may be the reason for humanity's exploring？
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