题目

   Last year, A Bite of China, made by CCTVs Documentary Channel, sparked discussion not only on Chinese food, but also on locally made documentary programs. When you think of documentaries, you may think of them as long, boring programs. But documentaries can be wonderful and bring stories from the real world into our homes. With fascinating footage（影片片段） and stories, documentaries encourage us to think about interesting issues we wouldn’t necessarily know about. So, what makes a good documentary, and what should we pay attention to when we watch one? Here, we offer a下列物质的水溶液不能使紫色石蕊试液变红的是（ ）A．稀硫酸B．氧化钙C．浓盐酸D．二氧化碳