Final answer:
Heraclitus posited that you cannot step into the same river twice, signifying that all things are in a state of constant change, which aligns with the physical characteristics of a river's ever-changing waters. The correct answer is A. River.
Step-by-step explanation:
Around 500 B.C., the philosopher Heraclitus made the famous assertion that change is constant, conveying the idea that one cannot step into the same river twice. This prominent quote captures Heraclitus's belief in the perpetual flux of the universe. The correct answer to the question is: A. River.
Rivers, by their very nature, are continuously moving bodies of water, originating from headwaters and flowing towards a lake or an ocean. The unceasing motion of a river exemplifies the concept Heraclitus was describing: its waters are always changing, making it a different river from moment to moment.
Heraclitus's observation about rivers not only represented his philosophical views on the transient nature of reality but also holds true in the physical sense, as rivers constantly carry fresh waters to their destinations, reshaping and renewing their contents continuously.