What type of current flow is opposed by resistance?

Resistance opposes the flow of electric current in all forms, including direct current (DC), alternating current (AC), and radio frequency (RF) current. This opposition is due to the physical properties of the materials through which the current is passing, which impedes the flow of charged particles and converts some of the energy into heat.

Direct current flows in one constant direction, while alternating current changes direction periodically. Both types of current face resistance, which affects their efficiency and the amount of power that can be delivered. RF current, which consists of alternating current at very high frequencies, is also subject to resistance in wiring and components used in RF applications.

Since resistance impacts the flow of all these types of current, the correct response encompasses all forms of current flow listed in the question, making "All these choices are correct" the appropriate answer.