（单选题）
Why does performance degrade when many UPDATE， INSERT， or DELETE statements are issued on a tablethat has an associated Bitmap index（）
AThe DML operations re-create the Bitmap index blocks.
BThe Bitmap index is rebuilt automatically after a DML operation.
CThe smallest amount of a bitmap that can be locked is a bitmap segment.
DAdditional time is taken to remove NULL values from the Bitmap index after a DML operation.
正确答案
答案解析
略
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