Option 1: Meher Chand Mahajan - Meher Chand Mahajan was the third Chief Justice of India, serving from 1951 to 1954. Therefore, option 1 is incorrect.
Option 2: M. Patanjali Sastri - M. Patanjali Sastri was the second Chief Justice of India, serving from 1950 to 1951. Therefore, option 2 is incorrect.
Option 3: Harilal Kania - Harilal Kania was the first Chief Justice of India. He assumed office on 26 January, 1950, the same day the Indian Constitution came into effect. Therefore, option 3 is the correct answer.
Option 4: B.K. Mukherjea - B.K. Mukherjea served as the Chief Justice of India from 1951 to 1954. Therefore, option 4 is incorrect.
In conclusion, the first Chief Justice of India who assumed office on 26 January, 1950, was Harilal Kania.