The correct answer is option 1, Ministry of Defence. The Border Roads Organization (BRO) is a government agency responsible for the construction and maintenance of roads and infrastructure in border areas of India. It primarily operates in areas that are strategically important for national security and defense purposes.

Option 2, Ministry of Road Transport and Highways, is incorrect. Although the BRO is involved in road construction and maintenance, it is not under the administrative control of the Ministry of Road Transport and Highways.

Option 3, Prime Minister`s Office, is also incorrect. While the BRO plays a crucial role in the defense and security of the nation, it does not directly fall under the administrative control of the Prime Minister`s Office.

Option 4, Indian Army, is partially correct. The BRO works closely with the Indian Army and is often referred to as the "lifeline of the armed forces." However, it is important to note that the BRO is not directly under the control of the Indian Army. Rather, it operates under the administrative control of the Ministry of Defence, which oversees both the Indian Army and the BRO.