Introduction:
Photosynthesis is the process by which plants, algae, and some bacteria convert light energy from the sun into chemical energy in the form of glucose. C3 and C4 plants are two different types of photosynthetic pathways found in plants. C4 plants are more efficient in photosynthesis than C3 plants due to various reasons.

Reasons for C4 plants being more efficient in photosynthesis:

Lowest rate of photorespiration:
Photorespiration is a process in which plants consume oxygen and release carbon dioxide in the presence of light. This process reduces the efficiency of photosynthesis. C4 plants have a lower rate of photorespiration than C3 plants because they have a unique anatomical and biochemical mechanism that separates the initial fixation of CO2 from the Calvin cycle. This separation reduces the amount of oxygen available for photorespiration, thereby increasing the efficiency of photosynthesis.

Higher leaf area:
C4 plants have a higher leaf area than C3 plants. This increased leaf area provides more surface area for photosynthesis, which leads to more efficient photosynthesis.

Presence of a large number of chloroplasts in the leaf cells:
C4 plants have a large number of chloroplasts in their leaf cells. Chloroplasts are the organelles responsible for photosynthesis. The presence of a large number of chloroplasts increases the efficiency of photosynthesis by providing more sites for the light-dependent reactions of photosynthesis.

Presence of thin cuticle:
C4 plants have a thinner cuticle than C3 plants. The cuticle is a waxy layer that covers the surface of leaves and protects them from water loss. A thin cuticle allows more light to penetrate the leaf and reach the chloroplasts, increasing the efficiency of photosynthesis.

Conclusion:
C4 plants are more efficient in photosynthesis than C3 plants due to various reasons, including a lower rate of photorespiration, higher leaf area, a large number of chloroplasts in the leaf cells, and a thin cuticle. These adaptations allow C4 plants to thrive in hot and dry environments where water is scarce.

Option A- lowest rate of photorespiration
bcoz these plants have not palisade tissue. instead of this tissue they have mesophyll tissue and specially they show kranz anatomy