The correct answer is option 'C) Megalithic burials'.

Megalithic burials refer to the practice of burying the dead in tombs or graves made of large stones or megaliths. These burials are found in various parts of the world and are known for their association with the use of iron tools and weapons. Some of the largest collections of iron tools and weapons have been discovered in megalithic burials.

1. Megalithic Burials:
Megalithic burials were a common practice in ancient societies, especially during the Bronze Age and Iron Age. These burials were built using large stones or megaliths and often included multiple chambers or passages. They were used to bury individuals or sometimes even entire communities.

2. Iron Tools and Weapons:
During the Iron Age, iron tools and weapons became more prevalent and replaced the use of bronze. Iron was stronger and more readily available, making it a preferred material for tools and weapons. Iron tools such as axes, hammers, and chisels, as well as weapons like swords and spears, were commonly used during this period.

3. Large Collections:
Some of the largest collections of iron tools and weapons have been found in megalithic burials. These burials were often associated with individuals of high social status or warriors, who were buried with their valuable possessions. The presence of a large number of iron tools and weapons in these burials indicates their importance and significance in the society of that time.

4. Significance:
The discovery of large collections of iron tools and weapons in megalithic burials provides valuable insights into the technological advancements and social structures of ancient societies. It suggests that iron tools and weapons were not only functional but also held symbolic and prestige value. These burials also indicate the presence of skilled metalworkers who were capable of producing such objects.

In conclusion, megalithic burials have been found to contain some of the largest collections of iron tools and weapons. These burials provide important archaeological evidence about the use of iron during the ancient times and shed light on the social and technological aspects of those societies.