Which of the following is a unit vector that points in the direction of the origin when its tail is placed on the point (x=2, y=3, z=4)?
a) 1/√29 <-2, -3, -4 >
b) 1/√29 <2, 3, 4 >
c) 1/√7 <-2, -3, -4 >
d) 1/√7 <2, 3, 4 >