Final answer:
The resistance of a superconductor decreases rapidly at the critical temperature, indicating a significant decrease in resistance. Therefore, the correct answer is b. Decreases rapidly.
Step-by-step explanation:
The resistance of a superconductor decreases rapidly at the critical temperature, making option b. Decreases rapidly the correct answer.
At the critical temperature (Tc), superconductors undergo a phase transition in which they lose all electrical resistance.
This behavior is depicted by a sharp drop in resistivity on a graph of resistivity vs. temperature for a superconductor. At temperatures below Tc, the resistivity falls to zero, indicating a significant decrease in resistance.
High temperature superconductors have critical temperatures above easily achievable temperatures, such as 77 K for liquid nitrogen. These materials exhibit a rapid decrease in resistance below their specific Tc.