The Sleep Heart Health Study Enrolled a Randomly Selected Cohort

The Sleep Heart Health Study enrolled a randomly selected cohort of 6294 adults not treated for sleep-disordered breathing. The men and women in the study were classified into four groups depending on the extent of their sleep-disordered breathing (none, mild, moderate, or severe) . Is there significant evidence that men and women differ in extent of their sleep-disordered breathing? Here is an incomplete Minitab output to help you answer this question.
Chi-Square Test:
Expected counts are printed below observed counts
Chi-Square contributions are printed below expected counts

$$\begin{array} { l r r r r r } & \text { none } & \text { mild } & \text { moderate } & \text { severe } & \text { Total } \\\\\text { women } & 2167 & 821 & 265 & 99 & 3352 \\& 1826.18 & 957.03 & 387.18 & & \\& 63.605 & 19.335 & 38.555 & & \\& & & & & \\\\\text { men } & 1262 & 976 & 462 & 242 & 2942 \\& 1602.82 & 839.97 & 339.82 & & \\& 72.469 & 22.029 & 43.928 & & \\\\\text { Total } & 3429 & 1797 & 727 & 341 & 6294\end{array}$$
What is the degrees of freedom for this chi-square test?

A) 3
B) 4
C) 6
D) 8