The correct answer is: a) English language and Western knowledge.
The colonial education system in Assam was designed to create a class of Indians who could serve the British Raj. The focus was on English language and Western knowledge, as these were seen as essential for the administration of the colony. Indigenous knowledge systems were largely ignored, and Assamese language and literature were not given much importance.
Option b) is incorrect because the colonial education system did not focus on preserving indigenous knowledge systems. In fact, many indigenous knowledge systems were suppressed by the British.
Option c) is incorrect because the colonial education system did not focus on promoting Assamese language and literature. In fact, Assamese language and literature were often seen as a threat to British rule, and were therefore discouraged.
Option d) is incorrect because the colonial education system did not focus on providing vocational training. The focus was on producing a class of Indians who could serve the British Raj in administrative and professional roles.