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 point of intersection.
B) intersect at a unique point.
C) intersect along a straight line.
D) intersect along a plane.