Red ink is prepared from:A. AnilineB. EosinC. PhenolD. Congo red

The correct answer is D. Congo red.

Explanation:
Congo red is a dye that is commonly used to produce red ink. It is an azo dye derived from the coupling of benzidine and naphthionic acid. When dissolved in water, it produces a vivid red color, making it suitable for use in inks and stains.

Here’s a brief overview of the other options:

A. Aniline: Aniline is an organic compound that is used to make dyes, but it is not directly used to make red ink. It can be used as a precursor in the synthesis of various dyes, including some that might be red, but it is not itself red ink.

B. Eosin: Eosin is a red dye often used in histology and as a fluorescent dye. While it is red, it is more commonly used for staining purposes rather than as a primary component of ink.

C. Phenol: Phenol is an aromatic compound that is not used to make red ink. It is used in the production of plastics, resins, and other chemicals, but not in dyeing.

In summary, Congo red is specifically recognized for its use in creating red ink, making option D the best choice.