单项选择题

According to the passage the low-Earth orbit is ______.

A．the destination for most commercial payloads
B．a few hundred kilometers above the earth
C．about 36,000 kilometers away above the earth
D．a few hundred kilometers above the stationary orbit

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单项选择题

What can be inferred from the passage

A．When traveling in space, spacecraft take indirect route to avoid gravity from other planets.
B．Space engineers are now developing space elevators.
C．It will take the current spacecraft several hundred years to travel to other solar systems.
D．Scientists from different countries are working together to develop new space technologies.

单项选择题

In 1994,the Carnegie Corporation released a report to ______.

A．advocate the importance of the early-year education
B．develop the education market for parents and children
C．emphasize parent's wise investment on children
D．explain in detail the science on networks of nerves