The correct answer is: b) Neolithic.
Polished stone axes are a distinctive artifact of the Neolithic period, which is also known as the New Stone Age. This period began around 10,000 years ago and lasted until around 4,500 years ago. It is characterized by the development of agriculture and the use of polished stone tools.
The Mesolithic period, or Middle Stone Age, began around 10,000 years ago and lasted until around 8,000 years ago. It is characterized by the transition from hunting and gathering to a more settled lifestyle. However, people in the Mesolithic period did not yet practice agriculture.
The Chalcolithic period, or Copper Age, began around 6,000 years ago and lasted until around 3,500 years ago. It is characterized by the development of metallurgy and the use of copper tools.
The Iron Age began around 3,000 years ago and lasted until around 1,500 years ago. It is characterized by the development of iron metallurgy and the use of iron tools.
In conclusion, polished stone axes are a distinctive artifact of the Neolithic period. They are not found in the Mesolithic, Chalcolithic, or Iron Ages.