[单选题]
At the first minima on either sik :; d.zei(dpsmqo,k ,de of the central bright spot in a double-se3l,g4tm(2q mg 1sit jlit experiment, light from each ope4 t3,lq memg2(t ij1sgning arrives
A. in phase.
B. $90^{\circ}$ out of phase.
C. $180^{\circ}$ out of phase.
D. none of the given answers
