The Kothari Commission suggested

The correct option is: That English be studied as a library language with the aim of getting the knowledge of science and technology, commerce and trade by reading standard books in English.

Step-by-Step Explanation:

1. Understanding the Kothari Commission (1964-1966):
The Kothari Commission, also known as the National Education Commission, was set up by the Government of India to examine all aspects of the educational sector in India and to evolve a general pattern of education. One of its key focus areas was language policy and the role of different languages in the educational system.

2. The Concept of "Library Language":
The Commission recognized that while regional languages should be the media of instruction at the school and higher education levels, English plays a vital role in accessing global knowledge. Thus, it recommended that English should be studied as a "library language."

3. Role and Purpose of a Library Language:
As a library language, the primary objective of teaching English is to enable students to read, comprehend, and acquire knowledge from standard literature, particularly in fields like science, technology, commerce, and international trade. This ensures that Indian students and researchers remain connected to global academic and scientific advancements without making English the sole medium of instruction or research.

4. Why other options are incorrect:
- The commission did not recommend using English as a link language solely to translate texts between Indian languages.
- It did not mandate that research in India must be done only in English.
- While university teachers are expected to be proficient, the specific institutional recommendation regarding the status of the language was its designation as a "library language" for acquiring knowledge from standard reference materials.