Let $P_{1},P_{2},$ and $P_{3}$ denote, respectively, the planes defined by
$a_{1}x + b_{1}y + c_{1}z = \alpha _{1}$
$a_{2}x + b_{2}y + c_{2}z = \alpha _{2}$
$a_{3}x + b_{3}y + c_{3}z = \alpha _{3}$
It is given that $P_{1},P_{2},$ and $P_{3}$ intersect exactly at one point when $\alpha _{1}= \alpha _{2}= \alpha _{3}=1$ . If now $\alpha _{1}=2, \alpha _{2}=3 \;and \; \alpha _{3}=4$ then the planes
(A) do not have any common point of intersection
(B) intersect at a unique point
(C) intersect along a straight line
(D) intersect along a plane