Brain drain refers to the large-scale emigration of highly trained and talented people from a country, particularly the movement of skilled scientists, doctors and academics abroad in search of better opportunities. The question asks which Education Commission of India first took serious note of this problem.

The Education Commission of India, popularly known as the Kothari Commission (1964 to 1966) and chaired by Dr. D. S. Kothari, was the first comprehensive commission to review the entire field of education in post-independence India and it drew serious attention to the problem of brain drain, the loss of trained manpower migrating out of the country. Since the option is worded exactly as The Education Commission of India, this refers to that landmark commission.

The University Education Commission (1948 to 1949) under Dr. S. Radhakrishnan dealt primarily with the reorganization of university-level education soon after independence and did not focus on brain drain, so it is not the answer.

The Calcutta University Commission (1917 to 1919), also called the Sadler Commission, functioned during the pre-independence colonial period and examined the problems of Calcutta University, so it is unrelated to the post-independence brain-drain issue.

The Sargent Commission (Sargent Report of 1944) was a pre-independence plan for the development of education in British India and again predates and does not address the brain-drain concern raised later.

Thus the commission that first seriously noted brain drain is the one named as the Education Commission of India.
Correct answer: The Education Commission of India