To distinguish between signal having very close values, we need an instrument with :

The correct answer is option 2

Concept:

1. High accuracy: Accuracy refers to how close a measurement is to the true value. While important for obtaining correct values, high accuracy alone doesn't guarantee the ability to distinguish between very close values. An instrument could be highly accurate but still not have the necessary level of detail to differentiate between closely spaced signals.

2. High resolution: Resolution is the smallest change in the measured quantity that an instrument can detect and display. An instrument with high resolution can distinguish between very small differences in the input signal. If the instrument has a high resolution, it can provide more detailed measurements, allowing us to differentiate between signals that are very close to each other.

3. High sensitivity: Sensitivity is the ratio of the output signal to the input signal. A highly sensitive instrument can detect very small changes in the input signal and produce a measurable output. While sensitivity is important for detecting weak signals, it doesn't directly address the ability to distinguish between signals that are very close in value. A highly sensitive instrument might amplify noise along with the signal, making it harder to discern closely spaced values.

4. High linearity: Linearity refers to the degree to which the output of an instrument is directly proportional to the input over a specified range. While important for accurate measurements across a range, it doesn't directly determine the ability to distinguish between closely spaced values.