A common theory about influenza is that it is a disease occurring primarily in cold weather. Doctors report incidences of illness such as influenza to the Centers for Disease Control (CDC). The graph

A common theory about influenza is that it is a disease occurring primarily in cold weather. Doctors report incidences of illness such as influenza to the Centers for Disease Control (CDC). The graph below shows data for three years. Note that this graph shows from October of one year to October of the following year. The leftmost data on the graph begins with week 40 (October) and shows data through the end of the year. The check mark for week 1 (beginning of January) is roughly in the middle of the x-axis. Which evidence supports this theory? The graph line for 2008-09 has several peaks. All three graph lines show different patterns throughout the year. The graph line for 2008-09 has a peak in week 17. All three graph lines peak over the same few weeks of winter.