What type of current flow is opposed by resistance?

Resistance is a fundamental property of materials that opposes the flow of electric charge, regardless of how that charge is moving. Therefore, it applies to all forms of electrical current. Whether the current flows continuously in one direction (Direct Current), reverses direction periodically (Alternating Current), or oscillates at radio frequencies (RF current), the electrons will always collide with atoms in the conductor, creating resistance. Students sometimes think resistance only applies to DC because they learn about impedance or reactance for AC and RF. While reactance also opposes AC and RF, pure resistance is still a factor in all of these current types, making 'All these choices are correct' the right answer.