Which of the following pigments is known for its ability to help control viscosity and flow in paint?

The correct choice is based on the function of extender pigments in paint formulations. Extender pigments, such as calcium carbonate or clay, are used to increase the bulk of the paint while also modifying its physical properties, including viscosity and flow characteristics. These pigments do not significantly alter the color but are essential for improving the paint's application qualities, making the paint easier to work with and enhancing its spreadability.

Rutile Titanium Dioxide, while an important pigment for providing opacity and brightness, primarily contributes to color rather than controlling viscosity. Filler pigments also play a role in thickening and improving texture, but they are generally used to fill space and improve the durability or texture rather than specifically to influence viscosity and flow. Organic pigments, on the other hand, are primarily used for their vibrant colors and are less effective at modifying flow properties compared to extender pigments. Thus, extender pigments are specifically recognized for their role in controlling paint viscosity and flow, making it the most appropriate answer.