Final answer:
The word 'fast' in the given sentence serves as an adjective, describing the noun 'life' and reflecting the speedy nature of modern living. Option (i) is correct.
Step-by-step explanation:
The word 'fast' in the sentence 'Modern man leads a fast life.' functions as an adjective. It describes the noun 'life,' providing information about the nature of modern life—specifically, that it is characterized by speed and busyness.
This is reflected in various contexts, such as the ever-accelerating pace of life due to advancements in technology, and the societal trends that encourage a lifestyle of constant activity and movement. The fact that modern life often involves social mixing, mobility, and a general hastening in activities underscores the usage of 'fast' as an adjective here.