The correct option is D 1
x∝y⇒x=k1y (k1 = non-zero varitaion constant )
⇒k1=xy...........................(1)
y∝z⇒y=k2z (k2 = non-zero varitaion constant )
⇒k2=yz...........................(2)
z∝x⇒z=k3x (k3 = non-zero varitaion constant )
⇒k3=zx...........................(3)
Now, multiplying (1),(2) and (3) we get, k1.k2.k3=xy×yz×zx
or, k1,k2,k3=1.
Hence the product of non-zero varitaion constant is 1.