The correct option is A independent of m and n
∣∣
∣
∣
∣∣xmn1axn1abx1abc1∣∣
∣
∣
∣∣=0
Applying R4→R4−R3 and expanding
∣∣
∣
∣
∣∣xmn1axn1abx100c−x0∣∣
∣
∣
∣∣=(c−x)∣∣
∣∣xm1ax1ab1∣∣
∣∣=0
Applying R3→R3−R2 and expanding
(c−x)∣∣
∣∣xm1ax1ab1∣∣
∣∣=(c−x)∣∣
∣∣xm1ax10b−x0∣∣
∣∣⇒(c−x)(b−x)(x−a)=0
Hence, roots of the quation are independent of m and n.