Researchers Are Interested in the Effects of Wind Direction and Season

Multiple Choice

Researchers are interested in the effects of wind direction and season on ozone levels in North America. The ozone levels were recorded at locations, along with the direction of prevailing winds (E, N, S, W) and the season (winter, spring, summer, fall) . A balanced design was carried out such that each combination was observed five times. A partial ANOVA table is provided here:
Upon rejecting the null hypothesis for the test of an effect due to season, what would be the correct interpretation of the true mean ozone level?
$$\begin{array} { l l l l l } \text { Source } & \text { DF } & \text { SS } & \text { MS } & \text { F } \\\hline \text { Direction } & & 129 & & \\\text { Season } & & 318 & & \\\text { Interaction } & & 423 & & \\\text { Error } & & 960 & \\\hline \text { C. Total } & & 1830\end{array}$$

A) It is different for all seasons.
B) It is not different for all seasons.
C) It is different for at least one pair of seasons.
D) It is different for all seasons, but only if wind direction is ignored.