Among the following leaders, who has served for the longest total period as the Prime Minister of India?

Introduction / Context:
The office of the Prime Minister of India is the most important position in the executive branch, and the duration of service of different Prime Ministers is a common topic in history and polity questions. This question asks you to identify which of the listed leaders held the office of Prime Minister for the longest total period, taking into account multiple terms if applicable. Knowing these durations helps in understanding the political history and stability of various governments in India.

Given Data / Assumptions:

The leaders listed are Jawaharlal Nehru, Indira Gandhi, Manmohan Singh and Lal Bahadur Shastri.
You are asked to choose the one who served for the greatest total number of years as Prime Minister.
It is assumed that you know approximate tenure periods for these leaders, particularly the long serving ones like Nehru and Indira Gandhi.

Concept / Approach:
Jawaharlal Nehru was the first Prime Minister of independent India and served from August 1947 until his death in May 1964, which is roughly seventeen years. Indira Gandhi served in two main stretches, from 1966 to 1977 and then from 1980 until her assassination in 1984, totalling around fifteen or sixteen years. Manmohan Singh served two consecutive terms from 2004 to 2014, amounting to about ten years. Lal Bahadur Shastri served a much shorter period from 1964 to 1966. Therefore, the correct approach is to compare these durations and identify Nehru as the longest serving Prime Minister among them.

Step-by-Step Solution:
Step 1: Consider Jawaharlal Nehru. He became Prime Minister in August 1947 and continued in office until May 1964. This is a continuous tenure of about seventeen years. Step 2: Consider Indira Gandhi. She served as Prime Minister from 1966 to 1977 and again from 1980 to 1984. Together, her time in office is around fifteen to sixteen years, slightly less than Nehru. Step 3: Consider Manmohan Singh. He served as Prime Minister from 2004 to 2014, which is ten years. Step 4: Consider Lal Bahadur Shastri, who served as Prime Minister from 1964 until his death in 1966, a relatively short tenure of about one and a half to two years. Step 5: Compare these durations. Nehru's tenure of about seventeen years is longer than Indira Gandhi's approximate fifteen to sixteen years, Manmohan Singh's ten years and Shastri's much shorter period. Step 6: Therefore, Jawaharlal Nehru is the leader who served the longest total period as Prime Minister among the given options.

Verification / Alternative check:
History and polity references consistently describe Jawaharlal Nehru as the longest serving Prime Minister of India. Chronological timelines of Indian Prime Ministers show his tenure from independence until 1964 without interruption. Indira Gandhi is often mentioned as having the second longest tenure. This pattern is widely accepted and appears in many examination guides, confirming that Nehru holds the record among the options given.

Why Other Options Are Wrong:
Indira Gandhi: Although she served for a very long period and is one of the longest serving Prime Ministers, her combined tenure is still shorter than Nehru's continuous time in office. Manmohan Singh: He served for two full terms of five years each, totalling ten years, which is significant but clearly less than both Nehru and Indira Gandhi. Lal Bahadur Shastri: His tenure was relatively brief due to his sudden death in office and cannot compare in length to the other three leaders listed.

Common Pitfalls:
Some learners may confuse longest continuous tenure with most number of terms or may not carefully add the periods of a leader who served non consecutively, such as Indira Gandhi. Others remember recent political figures more vividly and overestimate their duration. To avoid such mistakes, it helps to memorise approximate tenure lengths of key leaders: Nehru around seventeen years, Indira Gandhi around fifteen to sixteen years and Manmohan Singh ten years.

Final Answer:
Among the leaders listed, the person who served for the longest total period as Prime Minister of India is Jawaharlal Nehru.