[单选题]
If a wave from one slit of a Young's double slit experimenuuo qgo;h 7)n8) jrw-ht arrives aczwee++ib kzg+ ,*2ib q3jb6jt a point on the screen one-half wavelejeqb 2z,e i+6b+gci3zk+ *bwjngth behind the wave from the other slit, which is observed at that point?
A. bright fringe
B. dark fringe
C. gray fringe
D. multi-colored fringe