A depot manager argues: 'Nearly half our drivers cover fewer kilometres in a working day than the average driver at this depot. A driver who is below average is not up to the mark. So nearly half our drivers are not up to the mark.' The reasoning shifts the sense of one expression. Which of the following states that shift?

In its first use the expression records a position within the group, and some drivers must occupy it however good the whole group is. In its second use it becomes a verdict against a fixed standard. Sliding from the one to the other guarantees the manager's alarming finding no matter how well the depot performs, which is the surest sign that the word has changed its work. The other three expressions hold one sense throughout.