Torque/weight ratio of an instrument indicates sensitivity.

Explanation:
Torque/weight ratio is a measure of how sensitive an instrument is to the applied torque or force. It is calculated by dividing the torque produced by the instrument by its weight. The higher the torque/weight ratio, the more sensitive the instrument is.

Sensitivity is the ability of an instrument to detect small changes or variations in the input or output. In the case of torque/weight ratio, it refers to the instrument's ability to detect small changes in torque or force.

To understand why torque/weight ratio indicates sensitivity, let's consider a simple example. Suppose we have two instruments with different torque/weight ratios. Instrument A has a higher torque/weight ratio than Instrument B.

- Instrument A: Torque/Weight Ratio = 10 Nm/kg
- Instrument B: Torque/Weight Ratio = 5 Nm/kg

Now, if we apply the same force or torque to both instruments, Instrument A will produce a higher torque value compared to Instrument B. This means that Instrument A is more sensitive to the applied force or torque because it can detect smaller changes in the input.

The sensitivity of an instrument is an important characteristic in many engineering and scientific applications. It determines the instrument's ability to accurately measure and detect small changes in the physical quantity being measured.

For example, in a torque sensor used in automotive applications, a high torque/weight ratio indicates a more sensitive sensor that can accurately measure and detect small changes in engine torque. This information is crucial for various control systems in the vehicle, such as traction control and stability control.

In summary, the torque/weight ratio of an instrument indicates its sensitivity. A higher torque/weight ratio implies a more sensitive instrument that can detect small changes in torque or force. Therefore, the correct answer to the given question is option 'D' - sensitivity.