If f V and f R are the focal lengths of a convex lens for violet and red light respectively and F V and F R are the focal lengths of a concave lens for voilet and red light respectively, then we must have
A. fV > fR and FV > FR
B. fV < fR and FV > FR
C. fV > fR and FV < FR
D. fV < fR and FV < FR