单项选择题

After years of research, scientists have ______ the virus that is responsible for the disease.

A．recognized
B．identified
C．guaranteed
D．notified
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单项选择题
The ______ of rain forests may hamper a developing country in its fight against poverty.
A．reservation
B．preservation
C．conservation
D．compensation
单项选择题
Employers who establish retirement plans must be ______ about engaging in transactions with their plans.
A．indecisive
B．cautious
C．implicit
D．conscious
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