Carbon?

I am slowly developing a list of things I want to blog about and eventually they will be posted for your consideration. But until then I wanted to say that the weather is changing (sometimes erratically) and so the plants are beginning to emerge. The flower above is from a lupin plant and she was turned to the afternoon sun and the sea spray high on a windy cliff. All the physical parts of this plant are made from many different elements combined to make cellulose and lipids and proteins, among other things. But what interests me the most is that the sugars in this plant (like the cellulose, for example) are made of carbon. Many people don't fully appreciate how the plant gets (or acquires, if you will) this carbon. Do you know the answer to this question: "Plants are made of carbon. Where does that carbon come from?"

There are probably a million different ways to ask this question, but I'd like to point out that currently over half of my students (intro to biology students who are second and third year college students) did not give the correct answer.