Basic laboratory indicators for drinking water quality: identify the correct set of statements about colour, odour, and dissolved solids measurement.

Introduction / Context:
Rapid field and bench tests provide quick insight into aesthetic and operational qualities of raw and treated waters. Colour, odour, and conductivity are among the simplest indicators used by operators and labs.

Given Data / Assumptions:

• Visual comparison methods remain common for low-intensity colour measurement.
• Odour is evaluated qualitatively by threshold or intensity descriptors.
• Conductivity correlates with total dissolved solids (TDS).

Concept / Approach:
A tintometer (or colour comparator) measures small colour intensities by comparing against known standards. Odour is recorded using standard descriptors/intensity. Nessler tubes enable side-by-side visual comparison for colour or residual tests. Electrical conductivity relates to ionic strength and hence dissolved salt content.

Step-by-Step Solution:

Verification / Alternative check:
Standard methods texts include these procedures as routine preliminary assessments.

Why Other Options Are Wrong:
Each statement (a–d) is correct; therefore omitting any would reduce completeness. Hence (e) is the best comprehensive choice.

Common Pitfalls:
Confusing true colour vs. apparent colour; not filtering/treating samples appropriately before measurement.

Final Answer:
All of the above