选B
C(Cl^-)=1000pW/M=1000*1.18g/cm^3*3%/35.5=0.1mol
该溶液中C(Cu2+)=1/2C(Cl^-)=0.5mol
则300ml该溶液中n(Cu2+)=nV=0.5mol*0.3L=0.15mol