Evidence of rock-cut architecture in the context of the Harappa civilization was found in Dholavira, which is the correct answer (option B). Let's explore the details and significance of this finding:

Dholavira and Harappa Civilization:
Dholavira is an archaeological site located in the Kutch district of Gujarat, India. It is one of the five largest Harappan sites and was an important city of the ancient Indus Valley Civilization, also known as the Harappa Civilization. The civilization flourished around 2500 BCE to 1900 BCE in the northwestern regions of the Indian subcontinent.

Rock-Cut Architecture:
Rock-cut architecture refers to the method of creating structures by carving directly into natural rock formations. This technique was commonly used by ancient civilizations to create various structures like caves, temples, and reservoirs.

Evidence of Rock-Cut Architecture in Dholavira:
1. Reservoirs: One of the significant features of Dholavira is the presence of extensive water management systems, including large reservoirs. These reservoirs were built by cutting into the natural rock formations, showcasing the skill and knowledge of rock-cut architecture.

2. Water Channels: The city of Dholavira had a well-planned water supply system, with channels and embankments to direct and store water. Some of these channels were also carved into the rock, further demonstrating the use of rock-cut architecture techniques.

3. Stepwells: Dholavira is also known for its stepwells, which were used for water storage and as a means of accessing groundwater. These stepwells were intricately designed and constructed by cutting into the rock, providing evidence of the utilization of rock-cut architecture.

Significance of the Finding:
The discovery of rock-cut architecture in Dholavira has several implications for our understanding of the Harappa civilization and ancient Indian architecture:

1. Technological Advancements: The existence of rock-cut structures in Dholavira suggests that the Harappan people had advanced knowledge of engineering and construction techniques. They were able to carve into hard rock to create functional and elaborate structures.

2. Water Management: The presence of rock-cut reservoirs and channels highlights the importance of water management in the Harappa civilization. It indicates that the people of Dholavira had a sophisticated understanding of water conservation and storage.

3. Urban Planning: The use of rock-cut architecture in Dholavira, particularly in the water supply systems, indicates meticulous urban planning. The city was designed to efficiently manage water resources, which was crucial for the sustenance and growth of the civilization.

In conclusion, the evidence of rock-cut architecture in Dholavira provides valuable insights into the technological prowess, water management practices, and urban planning of the Harappa civilization. The discovery of these rock-cut structures at the site has contributed significantly to our understanding of ancient Indian architecture and the accomplishments of the Harappan people.