Assertion (A): Balban maintained cordial relationship with Mongols
Reason (R): The Mongol ruler, a grandson of Chengiz Khan, assured that Mongols would not advance beyond Sutlej.
(a) R is the correct explanation of A.
(b) R is not the correct explanation of A.
(c) A and R are wrong.
(d) A is wrong and R is the correct.