To increase the frictional force, it is necessary to:

Increasing the frictional force between two surfaces in contact can effectively be achieved by increasing the roughness of at least one of the surfaces. Frictional force arises from the interactions between the surfaces in contact, and rougher surfaces tend to have more microscopic interlocking features that can resist relative motion, thus increasing friction.

When at least one surface becomes rougher, it enhances the contact area and the interlocking between the surfaces, which directly contributes to a greater resistance to motion. This principle is foundational in understanding how friction works in various applications, from mechanical systems to material science.

While increasing the roughness of both surfaces (as mentioned in the second option) would indeed increase the frictional force, it is not a necessary condition—you can achieve sufficient friction simply by adjusting one of the surfaces. Similarly, increasing the speed of the moving body or applying a greater force parallel to the contact surfaces does not inherently increase the coefficient of friction; these factors can influence the force but do not address the fundamental mechanism of how friction itself can be increased through surface properties.