[单选题]
At the first minima on eithe+ afrnw5 1(wf k)v-qqg *71o cn:7newtm 0nigir side of the central bright spot in a double-slit experiment, light from each openinggn7o i:n*7 entw1im0c arrives
A. in phase.
B. $90^{\circ}$ out of phase.
C. $180^{\circ}$ out of phase.
D. none of the given answers
