What was the average number of female athletes who participated from country B over all the years together?

Answer: Option C

Average number of female athletes from B over all the years.
$$\begin{array}{rl}& =\frac{\left(4.2+6.2+4.8+8.4+5.2+7.2\right)\times 100}{6}\\ & =\frac{3600}{6}\\ & =600\end{array}$$