Which of the following is a chemical property of iodine?

D

Explanation:

From the graph, it is clear to see that the data reaches its peak somewhere around either December 7th or 8th. Since the only option that centers around these two dated is option D, we must assume this is our answer.

For further explanation, however, it is important to look at what the graph is telling us. If you look at the graph from where it starts to where it ends, you will note that there is a significant rise in the contaminants after December 4th, and the data continues to rise up until December 10th. Given that, it is easy to see how someone would mistakenly suggest that A would be the answer, but, as one can tell by examining the data closer, the graph clearly peaks at the 7th-8th day. This can only mean that the contaminants in the air peaked during that time frame.