The situation which is not possible about the pencils in her box is; Choice B: The longest pencil in the box is 8cm long.
By convention, the mean is a statistical measure of central tendency.
On this note, if the mean of a set of data values is 10, this means the data values have data points greater, equal and less than the mean value.
Read more on Mean;
https://brainly.com/question/281308