The correct option is A (1,1,1)
Normal vector of the plane is
→n=∣∣
∣
∣∣^i^j^k3−12123∣∣
∣
∣∣
=^i(−3−4)−^j(9−2)+^k(6+1)
=7(−^i−^j+^k)
∴ the equation of plane (→r) passing through the point (4,−1,2) is
(→r−→a)⋅→n=0
⇒(x−4)(−7)+(y+1)(−7)+(z−2)(7)=0
⇒x−4+y+1−z+2=0
⇒x+y−z−1=0
Clearly, point (1,1,1) lies on the plane