At the second minimum adjacent to the central maximum of a single-slit diffraction pattern the Huygens wavelet from the top of the slit is 180° out of phase with the wavelet from:
A. a point one-fourth of the slit width from the top
B. the midpoint of the slit
C. a point one-fourth of the slit width from the bottom of the slit
D. the bottom of the slit
E. none of these
