下列不属于热槽产生的原因的是：（）
A、冷槽不及时处理
B、极距过高或过低
C、铝水平和电解质水平低
D、电解质含碳或生成碳化铝
参考答案：D
—Has Tom gone to the zoo?
—Pardon?
—I asked _________ the zoo. [ ]
A. that Tom had gone to
B. Tom had gone to
C. has Tom gone to
D. if Tom had gone to
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