单项选择题

There is supposed to be a safety ______ which makes it impossible for trains to collide.

A．appliance
B．accessory
C．machine
D．mechanism
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单项选择题
______ something should go wrong, what would you do then
A．Supposing
B．Supposed
C．To be supposed
D．To suppose
单项选择题
I think we need to see an investment ______ before we make an expensive mistake.
A．guide
B．entrepreneur
C．consultant
D．assessor
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