Quadrilateral PQRS is a two-dimensional shape composed of four sides and four vertices. When it is reflected over the y-axis, the new quadrilateral created is P’Q’R’S’. By its definition, quadrilaterals are any closed figures with four straight sides and thus when reflecting this figure over the y-axis, all angles remain unchanged in terms of measure but simply move around to different positions within the new configuration. This means that whichever angle was previously largest will still have the greatest measure after reflection.

To further illustrate this concept, let’s consider an example of a square, which can be represented by Quadrilateral ABCD where each angle has a measure of 90 degrees. The resulting Quadrilateral A’B’C’D’ when reflected across the y-axis would have points A and D representing opposite corners on either side of it with an angle between them measuring 180 degrees.

Quadrilateral PQRS is reflected over the y-axis to create quadrilateral P’Q’R’S’. Which angle has the greatest measure?

Since we know all original angles measured 90 degrees each before being reflected across the y axis then we can infer that Angle AD or A’d has now become the greatest measured angle at 180 degrees while all other angles remain at 90 degrees each.

Thus in conclusion, whichever angle had the greatest measure prior to being reflected across a y axis will retain its status as having the greatest degree once reflections takes place; no new measures are introduced in such transformation processes involving reflection only shifts occur instead.