Six Second Grade Students Tried Tossing a Ball into a Basket

Six second grade students tried tossing a ball into a basket ten times each. Their teacher then suggested a different way of tossing the ball, and the six students tried again. The number of successful tosses, before and after the teacher's added instruction, are shown below.
$\begin{array}{|c|c|c|}\hline \text { Student } & \begin{array}{c}\text { Successful Tosses } \\\text { Before (out of 10) }\end{array} & \begin{array}{c}\text { Successful Tosses } \\\text { After (out of 10) }\end{array} \\\hline \text { A } & 4 & 5 \\\hline \text { B } & 3 & 3 \\\hline \text { C } & 5 & 1 \\\hline \text { D } & 4 & 5 \\\hline \text { E } & 5 & 1 \\\hline \text { F } & 3 & 3 \\\hline\end{array}$

Ignoring the differences of 0 , the (unsigned) rank of child $C$ is:

A) 4
B) 3.5
C) 3
D) 2.5