问题
选择题
The danger of 
HINI was real, especially in the beginning, little was known about the new disease.
A．if
B．because
C．when
D．before
答案
答案：C
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The danger of HINI was real, especially in the beginning, little was known about the new disease.
A．if
B．because
C．when
D．before
答案：C