Step 1: Understanding Chlorophyll's Role
Chlorophyll is the green pigment found in plants, which plays a vital role in the process of photosynthesis. Photosynthesis is the process by which plants convert light energy into chemical energy, producing glucose and oxygen. Chlorophyll absorbs light, mainly from the blue and red parts of the spectrum, and converts it into chemical energy.
Step 2: Why Other Options are Incorrect
- (B) Respiration: Chlorophyll is not involved in respiration, which occurs in the mitochondria of cells.
- (C) Excretion: Chlorophyll is not related to excretion. Excretion refers to the process of eliminating waste products, which is not a function of chlorophyll.
- (D) Transpiration: While chlorophyll is found in plants, transpiration is the process of water movement through plants and evaporation from aerial parts, which is not directly related to chlorophyll.
Thus, the correct answer is (A) for photosynthesis.
"Vanishing Greenery; A Growing Urban Crisis" In most of our cities, rapid urbanisation has led to a significant decrease in greenery over the past two decades. As the population increased, the demand for housing, roads and commercial buildings grew, leading to clearing of parks, gardens, and natural resources. This has contributed to several problems. 
(a) Mention one significant problem caused by the reduction in urban greenery.
(b) How do green plants contribute to improving the air quality?
(c) What role can you, as a citizen, play in protecting urban greenery?