View the Exhibit and examine the setting for a table. 
Which statement is true about the PCTFREE setting for the table?
A.It sets the minimum percentage of a data block to be reserved to contain chained rows from other
blocks.
B.It sets the minimum percentage of a data block to be reserved as free space before the server prevents inserts into the block.
C.It sets the minimum percentage of a data block to be reserved to contain the bitmap used to maintain the free block information.
D.It sets the minimum percentage of a block that can be used for row data plus overhead before new rows are added to the block.
PCTFREE 指的是为一个块保留的空间百分比，也就是什么情况下可以 insert，保留它的目的其实是为了给 update 保留空间，防止发生行迁移
A:错误,不是为了行链接
B:正确
C:错误，不是为了位图
D:错误