单项选择题
A.K<sub>2</sub>Cr<sub>2</sub>O<sub>7</sub>+浓H<sub>2</sub>SO<sub>4</sub>
B.K<sub>2</sub>Cr<sub>2</sub>O<sub>7</sub>+浓HCl
C.K<sub>2</sub>Cr<sub>2</sub>O<sub>4</sub>+浓H<sub>2</sub>SO<sub>4</sub>
D.K<sub>2</sub>Cr<sub>2</sub>O<sub>4</sub>+浓HCl