Where do you found the Dumb –bell-shaped guard cell?
A. Gymnosperms
B. Most dicots
C. Cereals
D. Xerophytes

Hint: Guard cell is the cells present in epidermis, leaves, and stem cells. These are present in pairs and with a gap between them that forms in stomatal pores. It helps in the control of the gas exchange. In most of the plants, it is a bean-shaped structure that opens and allows gas to enter into the stomata. In monocots, the guard cells are seen to be in different shapes.

Complete answer: Stomata are the tiny opening or pores found in the leaves and stems of some plants. These pores are bordered by specialized cells called Guard cells. These guard cells help in photosynthesis and also regulate water loss through transpiration. These guard cells contain chloroplast that helps in photosynthesis where sugar and energy are produced. When the guard cells are turgid, they open and allow the gas to enter. Mostly the guard cells are kidney-shaped in dicotyledon but in monocotyledon, it is Dumb bell-shaped.
In gymnosperms and xerophytes, the stomata are embedded deeply, they are not exposed to direct sunlight to check the excessive transpiration. This is called sunken stomata.
Here in this question, the monocotyledon is cereal.
So, the correct answer is “Option C”.

Additional Information:
The guard cells have a cytoplasmic lining, that contains chloroplast but the chloroplast has a very less capacity of photosynthesis due to the absence of an enzyme called rubisco. It is surrounded by accessory cells. The shape and size of stomata and guard cells vary from plant to plant.

Note:
Guard cells are the minute opening present in the epidermis of leaves and stem of the plants. It helps in the control of the gas exchange. The gap between them forms a stomatal pore. These help in the process of transpiration and regulate the water loss of plants. The guard cells are usually found in pairs. It is mostly found in kidney-shaped in dicotyledons and dumbbell-shaped in monocotyledon. In xerophytes and gymnosperms, to check the transpiration sunken stomata are present. In the members of Poaceae, Cyperaceae, and many palms, cereals it is dumb bell-shaped guard cells are found.