单项选择题

Scientists are ___ about the formation of coal.

A．confidential
B．confer
C．confident
D．conform
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单项选择题
We'll visit Australia next year __ we have enough money.
A．provided
B．unless
C．until
D．lest
单项选择题
Although I spoke to him many times, he never took any __ of what I said.
A．notice
B．warning
C．observation
D．attention
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