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[主观题]
The main purpose of the passage is toA．explain why it is important to invest in space rese
The main purpose of the passage is to
A．explain why it is important to invest in space research
B．explain how magnetic substorms interfere with satellite communications
C．define magnetic substorms and identify a recent scientific experiment to study them
D．compare two alternative approaches to the study of magnetic substorms
E．demonstrate that unmanned probes are the best way to conduct research in space
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