If the straight line \(\frac{x-x_0}{l}=\frac{y-y_0}{m}=\frac{z-z_0}{n}\) is parallel to the plane ax + by + cz + d = 0, then which one of the following is correct?
1
l + m + n = 0
2
a + b + c = 0
3
\(\frac{a}{l}+\frac{b}{m}+\frac{c}{n}=0\)
4
al + bm + cn = 0