The correct answer is: Both A and R are true but R is not the correct explanation of A.
Assertion (A) is true. Rajatarangini is a historical chronicle of the kings of Kashmir, written by Kalhana in Sanskrit. It is considered to be one of the most important sources of information on the history of Kashmir.
Reason (R) is also true. Historians do seek a lot of relevant information from Rajatarangini, as it contains year-wise facts about the kings of Kashmir. However, R is not the correct explanation of A. The reason why historians seek information from Rajatarangini is not because it contains year-wise facts, but because it is a valuable source of information on the history of Kashmir.
In conclusion, both A and R are true, but R is not the correct explanation of A.