问题描述：
If the virus of bird flu continues to grow at a fast speed,it could become a bigger ___ than SARS,which killed about 800 people last year.
a.question b.problem c.disease
为什么这里选A,而不是 B,怎么区别?
a.question b.problem c.disease
为什么这里选A,而不是 B,怎么区别?
问题解答：
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