[单选题]
If a wave from one slit oc +p rmu e7(wl8g lif;ari40.lf3 bn2i/snbz (g a Young's double slit experiment arrives at a point on the screen one-half wavelength behind the wave from the other slit, which is observed32s/nbi(nzg b at that point?
A. bright fringe
B. dark fringe
C. gray fringe
D. multi-colored fringe
