In colonial India, where was the first telegraph line in the country laid as a major communication link.

Introduction / Context:
The introduction of the electric telegraph in India was a major step in modern communication under British rule. Telegraph lines allowed the government to send messages quickly over long distances, which was crucial for administration, trade, and military control. This question asks about the route of the first telegraph line laid in India, a key fact in the history of technology and infrastructure in the country.

Given Data / Assumptions:

• The topic is the first telegraph line in India. • The question asks for the route of this initial line. • Options include several possible city pairs. • Calcutta was the capital of British India during the early telegraph period.

Concept / Approach:
The first major telegraph line in British India that is often asked in exams was laid between Calcutta and Agra. Lord Dalhousie strongly supported the telegraph system, and the line connecting Calcutta with Agra became operational in the early 1850s, linking the capital with an important inland city. Although there were experimental lines such as the one between Calcutta and Diamond Harbour, the exam standard answer for this question is Calcutta to Agra, which we should select.

Step-by-Step Solution:
Step 1: Recognise that the question is about the first telegraph line route that is usually highlighted in competitive exam material. Step 2: Recall that Calcutta, as the capital, was connected first to Agra through an approximately 800 mile line. Step 3: Check options. Agra to Jaipur, Delhi to Shimla, and Raniganj to Calcutta were later routes or not the main first line highlighted for exams. Step 4: Bombay to Thane is actually the first railway line in India, not a telegraph line. Step 5: Therefore, select Calcutta to Agra as the correct answer.

Verification / Alternative check:
General knowledge references for SSC and other exams consistently state that the first telegraph line in India was laid between Calcutta and Agra. Notes often mention that it was opened around 1854, and that telegraph technology allowed faster communication during events like the Revolt of 1857. Other routes listed in the options are either associated with later expansions of the telegraph or with different technologies such as railways. This makes Calcutta to Agra the standard and accepted answer.

Why Other Options Are Wrong:
Agra to Jaipur: This route could be part of later extensions, but it is not recorded as the first telegraph line in India. Delhi to Shimla: Important for colonial administration later on, especially when Shimla became the summer capital, but not the earliest line. Raniganj to Calcutta: Raniganj is associated primarily with coal and railway development; this route is not identified as the first telegraph line in standard exam material. Bombay to Thane: This was the route of the first passenger railway line in India in 1853, a different technology altogether and not a telegraph line.

Common Pitfalls:
A common mistake is to confuse the first railway line between Bombay and Thane with the first telegraph line and mark that option. Another confusion arises between experimental telegraph lines like Calcutta to Diamond Harbour and the first main line highlighted in exams, which is Calcutta to Agra. Students should clearly distinguish railways from telegraph lines and remember that the exam friendly formula is first telegraph line between Calcutta and Agra and first passenger railway line between Bombay and Thane.

Final Answer:
The first telegraph line in India was laid between Calcutta and Agra.