设z=x+yi,x,y∈R,∵
.
z (1+i)=2i,
∴( x-yi )(1+i)=2i,
化简可得 x+y+(x-y)i=2i,∴x+y=0 且x-y=2,
解得 x=1,y=-1,∴z=1-i,
故选 B.