Final answer:
During the plateau phase of a cardiac action potential, calcium conductance is greater than sodium and potassium conductance.
Step-by-step explanation:
The subject of this question pertains to the plateau phase of a cardiac action potential, which is a topic covered in high school biology. During the plateau phase, the calcium conductance is higher than the sodium and potassium conductance due to the prolonged opening of calcium channels. This influx of calcium is crucial for cardiac muscle contraction and maintains the action potential plateau. Chloride conductance is usually not a significant factor during this phase.
Therefore, the correct answer to the question about which conductance will be greater during the plateau phase is c) Calcium conductance.