[单选题]
At the first maxima on either sidc)p lty/mmlte.c( 0uep+ ztbc-0w kgy6 h+:w3e of the central bright d.1t2b if y+cpspot in a double-slit experiment, light from tc2dbyf+ i. 1peach opening arrives
A. in phase.
B. $90^{\circ}$ out of phase.
C. $180^{\circ}$ out of phase.
D. none of the given answers
