The correct answer is Option 4- 3000

The practice of erecting megaliths began about 3000 years ago. Megaliths are large stones that are used to construct structures, such as tombs, temples, and monuments. They are found in many parts of the world, including Europe, Asia, and Africa.

The earliest megaliths were built in Europe in the Neolithic period, which began around 10,000 years ago. The most famous example of Neolithic megaliths is Stonehenge, which is located in England. Stonehenge is a circular arrangement of stones that was built around 3000 BC.

Megaliths were also built in other parts of the world, such as Asia and Africa. In Asia, the most famous example of megaliths is the Moai statues, which are located on Easter Island. The Moai statues are giant human figures that were carved by the Rapa Nui people around 1200 AD.

The purpose of megaliths is still debated by archaeologists. Some believe that they were used as tombs, while others believe that they were used as temples or monuments. It is also possible that they served a variety of purposes.

The practice of erecting megaliths declined in the Iron Age, which began around 1200 BC. However, megaliths continue to be built in some parts of the world, such as New Guinea.