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单项选择题

What was NASA accused of on Wednesday

A．Being too prudent and cautious.
B．Being too hasty to assure safety.
C．Causing the Columbia tragedy.
D．Delaying launch plans.

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热门试题

单项选择题What did some scientists try to explain by suggesting that stars repel each other

A．Why stars move so quickly.
B．Why few stars have planets.
C．Why stars aren't moving toward one another.
D．Why stars haven't moved farther apart.

单项选择题What will the students read about for homework

A．Newton's life and times.
B．The influence of earlier scientists on Newton's ideas.
C．How gravity repels objects very close to each other.
D．How the current theory resolved contradictions in earlier ones.