Gram stain represents
a. A technique for staining bacteria and developed by Gram
b. A stain got from Gram
c. A cytochemical technique for differentiation of mitochondria
d. A trade name

Hint: Gram staining is the technique that is used to differentiate the large group of bacteria into two simple groups, based on the stain attained by the bacteria after the gram stain technique. The name of this stain was obtained after the discovery by Hans Gram.

Complete answer:
- This technique got this name, because of the scientist who discovered it, he is Hans Christian Gram.
- This stain differentiates the bacteria based on the physical and chemical properties of the cell wall.

> Technique:
- The smear is heat-fixed on the slide.
- Next, the primary stain, which they add is crystal violet and later iodine is added to fix the color
- Then after decolorization is made with ethanol and acetone.
- Then the counterstain is added which is safranin.
- The bacteria which retain the purple color of the crystal violet are considered as gram-positive and which attain the counterstain color such as pink or red color, they are called as gram-negative bacteria.
- The staining is mainly based on the peptidoglycan present in the cell wall of bacteria.
- In gram positive bacteria, the thick layer of peptidoglycan present, which retains the crystal violet. And in gram negative bacteria, a thin layer of peptidoglycan present, so it’s lost the primary stain by adding ethanol.

Hence, the correct answer is option (A).

Additional information:
- Reagents required for gram staining are,
- Crystal Violet – primary stain.
- Iodine solution- That fixes the crystal violet to cell wall
- Ethanol – decolorizer.
- Sarfarine- secondary stain.
- water.

Note: There are some other type of bacteria, called as gram intermediate, where they won’t respond to gram stain, some of the examples of this type are Mycobacterium Tuberculosis, Mycobacterium Leprae, Mycobacterium Bovis.