题干
（2016•恩施州）-- Where is your father?
-- I don't know, but he _______ the car when I left just now.
A：is washing
B：washed
C：was washing
答案(点此获取答案解析）
C
（2016•恩施州）-- Where is your father?
-- I don't know, but he _______ the car when I left just now.
A：is washing
B：washed
C：was washing
3I2+3H2O。根据此反应，可用试纸和一些生活中常见的物质进行实验，证明在食盐中存在IO3－。可供选用的物质有：①自来水；②蓝色石蕊试纸；③碘化钾淀汾试纸；④淀粉；⑤食糖；⑥食醋；⑦白酒。进行上述实验时必须使用的物质是（ ）