Does Fibrolytic Enzyme Level in Feedlot Cattle Affect Cattle Weight

Multiple Choice

Does fibrolytic enzyme level in feedlot cattle affect cattle weight gain, on average? Researchers randomly assigned 20 feedlot cattle to four groups, with each group being fed a diet containing a different enzyme level. Cattle weight gain (in kilograms) was recorded over the time of the study. There was no obvious deviation from Normality for these data. The findings are summarized below:
What are the degrees of freedom for the appropriate ANOVA test?
$$\begin{array} { | l | l | l | l | } \hline \text { Enzyme level } & n & \text { mean } & \text { std. dev. } \\\hline \text { None } & 5 & 51.8 & 4.9 \\\hline \text { Low } & 5 & 55.0 & 7.8 \\\hline \text { Medium } & 5 & 67.4 & 9.6 \\\hline \text { High } & 5 & 48.8 & 7.3 \\\hline\end{array}$$

A) 3 and 4
B) 3 and 16
C) 4 and 5
D) 4 and 20