The correct answer is c- Dye binding colorimetric method.

The determination of total protein in cerebrospinal fluid (CSF) is an important diagnostic tool in the evaluation of neurological disorders. The most commonly used method for this purpose is the dye-binding colorimetric method. This method involves the use of dyes such as Biuret reagent or Bradford reagent, which bind to the protein molecules and produce a color change that can be measured spectrophotometrically.

The Biuret reagent method is based on the formation of a complex between copper ions and peptide bonds in the protein molecule. The amount of copper ions that react with the protein is proportional to the amount of protein present in the sample. The color change produced by this reaction is measured at a wavelength of 540 nm.

The Bradford reagent method is based on the binding of Coomassie Brilliant Blue dye to the amino acid residues in the protein molecule. The amount of dye that binds to the protein is proportional to the amount of protein present in the sample. The color change produced by this reaction is measured at a wavelength of 595 nm.

Both methods are reliable and widely used for the determination of total protein in CSF samples. However, the dye-binding colorimetric method is preferred over other methods such as radioimmunoassay and protein electrophoresis, as it is simple, rapid, and cost-effective.

References:
1. Goldstein NP, Kattah JC. Cerebrospinal Fluid Analysis. [Updated 2021 Jul 6]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK459237/
2. Burtis CA, Ashwood ER, Bruns DE. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 5th ed. St. Louis, Mo: Elsevier Saunders; 2012.