66.
The answer is: D
Explanation
The correct option is D: 1st September, 1872.
This is the date when the Indian Evidence Act, 1872 came into force, as stated in section 1 of the Act12. The other options are incorrect because:
A: 6th October, 1860 is the date when the Indian Penal Code, 1860 came into force, not the Indian Evidence Act.
B: 1st March, 1974 is the date when the Code of Criminal Procedure, 1973 came into force, not the Indian Evidence Act.
C: 15th March, 1872 is the date when the Indian Evidence Act, 1872 was enacted by the Governor-General in Council, but it did not come into force until 1st September, 18723.