In which direction is the delta-v applied to change the orientation of the orbital plane?

A)
Parallel to the plane of orbit
B)
Tangent to the plane of orbit
C)
At an angle to the plane of orbit
D)
Perpendicular to the plane of orbit

Correct Answer :   Perpendicular to the plane of orbit


Explanation : The velocity change delta-v component perpendicular to the plane of orbit changes the orientation of the orbital plane. The velocity can change the size, shape or even rotate the line of apsides.