游乐园经营单位应当设置（），保持游览路线和入口的畅通，及时做好游览疏导工作。
A. 游乐引导标志
B. 指路标志
C. 出入口标志
D. 导向标志
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试验的试件加工中，块体材料也在不同部位取样混合后，取必要数量加工成（）送验。
A. 正方体块
B. 必须的尺寸
C. 多棱形状
D. 长方体尺寸
如果我们需要为用户提供DSL接入服务的话，那么必须拿掉用户线路上的负载线圈。（）
A. 对
B. 错
对一条河流来说，随着季节的不同，水位有所涨落，故航道尺度也会随之而发生变化。
A. 正确
B. 错误
In which cases is reference partitioning effective in enhancing performance？（）
A. It is effective only in partition pruning.
B. It is effective only in partitionwise joins provided that the query predicates are different from the partitioning key.
C. It is effective in both partition pruning as well as partitionwise joins provided that the query predicates are identical to the partitioning key.
D. It is effective in both partition pruning as well as partitionwise joins irrespective of whether the query predicates are different from or identical to the partitioning key.
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