Which teacher exhibition the most variable year to year performance over this 5 year span

Ed

Explanation:

As per the performance ratings presented in the graphic chart, 'Ed' is the teacher who displays the most variable or fluctuating during these five years. His performance has remained shifting constantly from (1 to 4 between 2005-06, then from 4 to 2 between 2006-07, and again 2 to 4 in 2007-08 and 4 to 1 in 2008-09). On the contrary, the other teachers have been able to remain consistent for once at least.

This observation validates the point that Ed has remained most inconsistent and exhibits the most variation during this span of five-years.

2nd option

explanation:

the bottom of the ocean