How is pressure built inside a Rotary Vane pump?

In a Rotary Vane pump, pressure is generated as the vanes make contact with the pump housing and the fluid being pumped. As the rotor turns, the geometry of the pump causes the space between the vanes to decrease as it approaches the discharge port.

When the vanes rotate, they create a vacuum in the larger chamber on the inlet side, causing fluid to enter. As the rotor continues to turn, the spaces between the vanes (the chambers) become smaller, which effectively compresses the water. This reduction in volume leads to an increase in pressure, allowing the fluid to be expelled from the discharge port at a higher pressure than it was introduced at the inlet.

Therefore, option C correctly describes the mechanism by which pressure is built in a Rotary Vane pump, as the vanes indeed become smaller near the discharge, facilitating the compression of fluid and thus generating pressure.