问题
选择题
Although the causes of cancer , we do not yet have any practical way to prevent it． [ ]
A．are being uncovered
B．have been uncovering
C．are uncovering
D．have uncovered
答案
答案：A
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Although the causes of cancer , we do not yet have any practical way to prevent it． [ ]
A．are being uncovered
B．have been uncovering
C．are uncovering
D．have uncovered
答案：A