z=(√3+i)/[1-√3i)²]
=(√3+i)/(-2-2√3i)
=-(√3+i)/[2(1+√3i)]
=-(√3+i)(1-√3i)/4
=-(2√3-2i)/4
=-(√3-i)/4
|z|=(1/4)√[(√3)²+(-1)²]=2/4=1/2
选B