The correct answer is C. Sensitivity.
Sensitivity is the ratio of the output of a system to the input. In the case of a recording system, the output is the deflection of the recorded trace, and the input is the input voltage. The sensitivity of a recording system is therefore the magnitude of the input voltage required to produce a standard deflection in the recorded trace.
Accuracy is the degree of conformity of a measured or calculated value to the actual or true value. Linearity is the degree to which a system’s output is proportional to its input. Resolution is the smallest change in input that can be detected by a system.
In conclusion, the sensitivity of a recording system is the magnitude of the input voltage required to produce a standard deflection in the recorded trace.