Hi,
(-a,b) and(-b,a) are in the same quadrant. So, a and b must be of the same sign. So, these points can both be in Q2 in a,b > 0
or Q4 if a,b < 0
From(1): xy>0
So, x and y are of same sign.
So,(-x,y) will be in Q2 in x,y > 0
or Q4 if x,y < 0
Not sufficient
From(2): ax>0
So, either both a,x >0 or both a,x <0
No info. about y
Not sufficient

Both (1)&(2):
a,b,x,y should be of the same sign.
Then (-x,y) will be in the same quadrant as (-a,b) (-b,a) are.
Sufficient

Hence, C

for (x,y) positive quadrant is 2nd
for (x,y) negative quadrant is 4th

x,y cannot be one positive and one negative. hence 3rd and 1st quadrant not considered.

1 x,y both positive then same quadrant.
x,y where x>0 and y<0 quadrant changes. Not sufficient.

2. same as above. not sufficient.


1+2 a,b and x,y are of same signs. thus they will be either in quadrant 2nd or 4th.

sufficient.
hence C.