The correctness of the statements can be analyzed as follows:

Statement 1: Dr. Rajendra Prasad, even though being an important figure in India`s struggle for independence, wasn`t responsible for persuading Mahatma Gandhi to come to Champaran to investigate the problem of peasants. It was actually Raj Kumar Shukla, a local influential indigo cultivator who brought Gandhi`s attention to the plight of peasants in Champaran. Thus, statement 1 is incorrect.

Statement 2: Acharya J.B. Kriplani was indeed one of Mahatma Gandhi`s colleagues in his Champaran investigation. Kriplani was one of the many fellow nationalists who supported and worked with Gandhi during this event. Therefore, statement 2 is correct.

Thus, among the provided options, option 2 which states "2 only" is the correct answer as it correctly identifies that the only true statement among the given options is statement 2.