The correct sequence of events relating to identifying the number of poor in India is as follows:

(D) Dadabhai Naoroji formulated the 'Jail cost of living.'

 (C) Planning Commission formed a study group. 

(A) Task force on projection of minimum needs and effective demand formed. 

(B) Expert groups formed.

So, the correct answer is (4) (D), (C), (A), (B).

The reason for the sequence of events relating to identifying the number of poor in India is as follows:

1.Dadabhai Naoroji formulated the 'Jail cost of living': This historical event represents one of the earliest attempts to understand and quantify the cost of living, which is essential for assessing poverty levels.

2.Planning Commission formed a study group: The Planning Commission was instrumental in conducting comprehensive studies and analyses to assess poverty levels and develop poverty estimation methodologies.

3 Expert groups formed: Expert groups were often assembled to provide their insights and recommendations for improving the accuracy and comprehensiveness of poverty estimation. 

4 Task force on projection of minimum needs and effective demand formed: Task forces and committees were established to work on refining the methodology for estimating poverty and projecting minimum needs for the population.

This sequence illustrates the progression of efforts and initiatives in India to identify and assess the number of people living in poverty, highlighting the historical context and evolving methodologies.