1. The statement 'Humans became food-producers during the New Stone Age', is true.
Explanation: Early humans were hunter-gatherers. They lived a nomadic life, moved from one place to another in search of food, water and shelter. In the New Stone Age, which extended from 8,000 BC to 4,000 BC, the humans started producing food. They lived a settled life, built houses near the fields, domesticated animals. This brought about a change in the way of life of the early humans.
2. The statement 'The quality of pottery improved after the wheel was invented ', is true.
Explanation: The invention of the potter's wheel proved to be helpful to the early humans. It made making pots convenient. The clay could be moulded in various shapes and sizes with help of the wheel.
3. The statement 'The discovery of charred grains and sickles at a site indicates that people living there practised agriculture ', is true.
Explanation: Charred grains and sickles had been found on sites. This proves that agriculture was practised. The early humans shifted from hunting-gathering to agriculture. Wheat and barley were the first crops to be cultivated.
4. The statement 'Only stone tools were made during the Chalcolithic period' , is false.
Explanation: The Chalcolithic period is also known as Copper-Stone Age. Tools were made of stone as well as copper. This was because copper is stronger than stone and lasts for a longer time.