To answer this question, we need to understand the historical context of the Chera Kingdom.
The Chera Kingdom was an ancient kingdom that existed in South India, specifically in the region known as Kerala. Therefore, the correct answer is D) Kerala.
Let's go through each option:
A) North east frontier - The Chera Kingdom did not rule in the north-eastern frontier. This option is incorrect.
B) Tamilanadu - The Chera Kingdom was located in the region of Kerala, which is separate from Tamil Nadu. This option is incorrect.
C) Karnataka - The Chera Kingdom did not extend into the region of Karnataka. This option is incorrect.
D) Kerala - The Chera Kingdom ruled in the region of Kerala. This option is correct.
Therefore, the correct answer is D) Kerala.