The most appropriate method of making egg-albumin sol is:

We start by recalling that a “sol” is a colloidal dispersion in which the dispersed phase is solid (here, protein molecules of egg albumin) and the dispersion medium is a liquid (here, saline water). To obtain a true sol, the protein must remain in its native, un-coagulated state; heating the protein will denature it, causing coagulation and converting it into a rubbery mass that cannot be redispersed into a colloidal system.

Now let us examine what part of the egg actually contains albumin. The transparent, viscous “egg white” (also called the albumen) is rich in albumin proteins, whereas the yellow “yolk” contains lipids, lecithin, and different proteins but is not the preferred source when our aim is to prepare an albumin sol. Hence, we must start with the white portion and we must keep it unheated.

Next, we think about how to maintain the proteins in dispersed form. A dilute sodium chloride solution (physiological saline, about 0.85 % w/V) or any mild 5 % w/V saline, provides ionic strength that helps the albumin molecules stay separate due to electrostatic repulsion. Therefore, the correct technique is to take the raw, transparent egg white and gently stir or shake it into a measured volume of 5 % saline so that the proteins are mechanically broken into colloidal-sized aggregates without being chemically or thermally denatured.

Let us now scrutinize each option:

A. The procedure says, “Break an egg carefully and transfer the transparent part (egg white) to 100 mL of 5 % w/V saline solution and stir well.” This matches exactly the requirements we just established: (i) use the albumin-rich white, (ii) do not heat, and (iii) disperse it directly into saline. So Option A is scientifically sound.

B. This option instructs us to boil the egg for 10 minutes, remove the shell, use the yellow part, and then homogenize. Boiling for 10 minutes will coagulate both the white and the yolk; once coagulated, proteins cannot be re-dispersed into a sol. Moreover, the yellow part is not albumin-rich. Hence, Option B is unsuitable.

C. This option again involves boiling for 10 minutes, but this time it uses the white part. Even though the white part originally contains albumin, heating for that long causes irreversible denaturation, so the product cannot form a sol. Therefore, Option C is incorrect.

D. This option suggests using the raw yellow part (yolk) without heating. Although the yolk is raw here, yolk constituents are mainly lipoproteins and fats, not albumin proteins of the type typically used in laboratory sols. Consequently, Option D will not give an egg-albumin sol.

Comparing all four possibilities, only Option A satisfies every criterion: (1) it employs the albumin-rich egg white, (2) it avoids thermal denaturation, and (3) it disperses the protein gently into a suitable ionic medium. Therefore, Option A is the most appropriate method.

Hence, the correct answer is Option A.