The correct option is B -1
The general form of linear equation written as,
a1x+b1y+c1=0
a2x+b2y+c2=0
Add comparing the coefficients of the variables, we find the value of k
x+ky=1 ---- (1)
x−y=2 ---- (2)
a1=1;b1=k;c1=1
a2=1;b2=−1;c1=2
a1a2=b1b2=c1c2
11=k−1
k=−1