[单项选择]Space enthusiasts look to the day when ordinary people, as well as professional astronauts and members of Congress, can leave Earth behind and head for a space station resort, or maybe a base on the moon or Mars. The Space Transportation Association, an industry lobbying group, recently created a division devoted to promoting space tourism, which it sees as a viable way to spur economic development beyond Earth.
The great stumbling block in this road to stars, however, is the sheer difficulty of getting anywhere in space. Merely achieving orbit is an expensive and risky proposition. Current space propulsion technologies make it a stretch to send probes to distant destinations within the solar system. Spacecraft have to follow multi-laver, indirect trajectories that loop around several planes in order to gain velocity from gravity assists. Then the craft lack the energy to come back. Sending spacecraft to other solar systems would take many centuries.
Fortunately, engineers ha
A. there is no clear destination in space
B. it is too risky and expensive for people to go beyond the orbit
C. the current space propulsion systems can not meet the needs for the long space travel
D. there is not enough energy for spacecraft to gain velocity

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[单项选择]Space enthusiasts look to the day when ordinary people, as well as professional astronauts and members of Congress, can leave Earth behind and head for a space station resort, or maybe a base on the moon or Mars. The Space Transportation Association, an industry lobbying group, recently created a division devoted to promoting space tourism, which it sees as a viable way to spur economic development beyond Earth.
The great stumbling block in this road to stars, however, is the sheer difficulty of getting anywhere in space. Merely achieving orbit is an expensive and risky proposition. Current space propulsion technologies make it a stretch to send probes to distant destinations within the solar system. Spacecraft have to follow multi-laver, indirect trajectories that loop around several planes in order to gain velocity from gravity assists. Then the craft lack the energy to come back. Sending spacecraft to other solar systems would take many centuries.
Fortunately, engineers ha
A. the development of space technology
B. the obstacles and prospects of space transportation
C. the public interests in space travel
D. the growth of space business

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[单项选择]Text 4

Space enthusiasts look to the day when ordinary people, as well as professional astronauts and members of Congress, can leave Earth behind and head for a space station resort, or maybe a base on the moon or Mars. The Space Transportation Association, an industry lobbying group, recently created a division devoted to promoting space tourism, which it sees as a viable way to spur economic development beyond Earth.
The great stumbling block in this road to stars, however, is the sheer difficulty of getting anywhere in space. Merely achieving orbit is an expensive and risky proposition. Current space propulsion technologies make it a stretch to send probes to distant destinations within the solar system. Spacecraft have to follow multi-laver, indirect trajectories that loop around several planes in order to gain velocity from gravity ass
A. the development of space technology
B. the obstacles and prospects of space transportation
C. the public interests in space travel
D. the growth of space business

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[填空题]Jim had a very ______ (disappoint) look when Tom told him Mary was not coming.

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[填空题]John had a (disappoint)______look when he was told not to go to the party.

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[填空题]Daylight Saving Time (DST)

How and When Did Daylight Saving Time Start
A．Benjamin Franklin-of "early to bed and early to rise" fame-was apparently the first person to suggest the concept of daylight savings. While serving as U.S. ambassador to France in Pads, Franklin wrote of being awakened at 6 a.m. and realizing, to his surprise, that the sun would rise far earlier than he usually did. Imagine the resources that might be saved if he and others rose before noon and burned less midnight oil, Franklin, tongue half in cheek, wrote to a newspaper.
B．It wasn’t until World War I that daylight savings were realized on a grand scale. Germany was the first state to adopt the time changes, to reduce artificial lighting and thereby save coal for the war effort. Friends and foes soon followed suit. In the U.S. a federal law standardized the yearly start and end of daylight saving time in 1918-for the states that ch

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