单项选择题

The management system of the rapid transit rail lines ______.

A．is already quite developed
B．does not exist at all
C．is not good enough
D．needs to include the strict guidelines
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LOGO is unique because ______.
A．it is an educational program
B．it is in total control of human beings
C．it allows children to teach the computer to think
D．children use it
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On what does the efficiency of a nation depend
A．Every individual.
B．Its machines.
C．Its wealth.
D．Its power.
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