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【单选题】
过渡元素高价化合物在酸性条件下有较强的氧化性，如KMnO 4 、Na 2 WO 4 （钨酸钠）等，钨的最高价为+6价。现有钨酸钠晶体（Na 2 WO 4 ·2 H 2 O）0.990g加水溶解后，再加入一定量的 锌和稀H 2 SO 4 ，反应生成一种蓝色化合物（可看作含+5价、+6价混合价态的钨的氧化物）且无H 2 产生。现用0.044mol/L KMnO 4 酸性溶液滴定这种蓝色化合物恰好将其氧化为一种黄色化合物，KMnO 4 中的+7价锰被还原成Mn 2+ ,共耗去KMnO 4 酸性溶液8.20mL（已知在酸性条件下氧化性；KMnO 4 >+6价的W的化合物）。上述蓝色化合物是A.
W 10 O 21
B.
W 8 O 22
C.
W 10 O 27
D.
W 5 O 14
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【单选题】Which one is wrong about classification and regression?
A.
Regression analysis is a statistical methodology that is most often used for numeric prediction.
B.
We can construct classification models (functions) without some training examples.
C.
Classification predicts categorical (discrete, unordered) labels.
D.
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